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Prof. Lloyd: Chemotherapy treatment of lymphoma in cats (RIP Scruffy)

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Prof. Lloyd: Chemotherapy treatment of lymphoma in cats (RIP Scruffy)

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Sugar Substitutes Affect Gut Health, so are they really healthier than regular natural sugar or is that what diet culture wants us to believe?

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As Diet Coke and its sweetener aspartame wrap up 40 years or so on American store shelves, the decades-long controversy around the safety of sugar substitutes continues. Ever since diet drinks hit the stores in the 1950s, rumors have swirled that such sweeteners-which today also include saccharin, sucralose and stevia-do more than satisfy a sweet tooth without the calories of sugar. But whether that "more" exists hasn't been easy to establish.

In a new study of four sugar substitutes, researchers found that these nonnutritive sweeteners don't just travel through the body unnoticed. The study results, published on August 19 in Cell, link two of the sweeteners-saccharin and sucralose-to spikes in glucose levels and suggest all four are tied to a shift in gut microbe profiles. Whether these findings translate into trouble, benefit or neither remains to be seen, and aficionados of diet drinks don't need to trash the diet soda can just yet.

"It's cool science and was very well designed, thought out and executed," says Dylan Mackay, an assistant professor of nutrition and chronic disease at the University of Manitoba, who was not involved in the study. "I've always wanted to do these more at-home trials, and they were able to pull it off in a really interesting way."

In 2014 researchers found a link between microbiome changes and blood glucose responses in mice after intake of sugar substitutes. To see if those same links applied to humans in the new study, the scientists selected participants from a potential pool of more than 1,375people, ruling out anyone who consumed noncaloric sweeteners in their regular daily life. Some had unknowingly done so by way of protein powders, chewing gum, or low-sugar snacks or desserts.

The researchers split the final 120 participants into six groups of 20. In four of these groups, participants consumed commercial packets of one of the four sweeteners at levels below their federal daily limit. A fifth group consumed only the filler used in these packets, which is commonly added to bulk out the tiny amount of sugar substitute they contain. The sixth group had no intervention.

During the two weeks that participants consumed their assigned sweetener or the filler, they also took oral glucose tolerance tests, which are used to measure the body's response to sugar and can be employed to diagnose some forms of diabetes. For these tests, they drank a glucose solution every morning after overnight fasting and used home-based continuous glucose monitors to track their blood glucose levels. The researchers also collected oral and stool samples from the participants to analyze the species of microbes they hosted. Study investigators additionally measured levels of some products of metabolism in the blood.

The participants who consumed saccharin or sucralose had a steeper blood glucose response than any of the other groups. When participants consumed any of the four sugar substitutes, their gut bacteria profile changed during the two weeks of intake. Along with these changes, levels of the metabolic products changed, too. For example, in participants who took saccharin, the production of a type of amino acid increased,echoing patterns seen in people with diabetes.

To confirm a link between microbial profiles and blood glucose responses, the investigators orally administered microbiomes-taken from the human participants with the highest and lowest blood glucose spikes following sweetener consumption-to germ-free mice. Mice exposed to microbiomes from human "top responders" showed changes in their blood glucose that "very significantly mirrored those of the donor individuals," says study author Eran Elinav, principal investigator of the Host-Microbiome Interaction Research Group at the Weizmann Institute of Science in Rehovot, Israel, and director of the Microbiome and Cancer Division at the German National Cancer Center in Heidelberg.

This part of the work "is a really cool portion of the paper," Mackay says. The findings in mice "are interesting mechanistic evidence that maybe [these sweeteners] are having an effect."

The effects of the sweeteners on blood glucose are likely highly personalized, Elinav says. But the results suggest these compounds don't just pass through the body, as some originally thought.

Part of the personalized response will relate to the health of the person involved, Mackay says. The findings "can't extend to people who may be overweight or have obesity or impaired glucose tolerance or type 1 or type 2 diabetes," he says.

The findings don't settle the question of whether any effects will be meaningful for human health-a subject to tackle in other studies, Elinav says. The researchers also don't know if these effects will persist beyond the two weeks of exposure in the current study, Mackay says.

The study involved healthy people without overweight or obesity and who represent only a subset of the population that consumes food and drink with these sugar substitutes, Mackay notes. "From a user perspective, as someone with type 1 diabetes, almost everything I use has aspartame," he says. "I'm not going to stop that and switch back to regular glucose or sugar-containing products because of these results."

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Some Sugar Substitutes Affect Blood Glucose and Gut Bacteria

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As Diet Coke and its sweetener aspartame wrap up 40 years or so on American store shelves, the decades-long controversy around the safety of sugar substitutes continues. Ever since diet drinks hit the stores in the 1950s, rumors have swirled that such sweeteners-which today also include saccharin, sucralose and stevia-do more than satisfy a sweet tooth without the calories of sugar.

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Grace Hartman: Compressions affect on the body

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Grace Hartman: Compressions affect on the body

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As a runner we are told to wear compression for our shins, but could it help with other things as well? What are some possible long term health effects of wearing compression?

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Stomach cramps and the urgent need for the toilet on long runs may partly be caused by decreased blood flow damaging gut cells. Compression socks reduce signs of this damage in marathon runners

Wearing compression socks may reduce the intestinal damage thought to cause cramping, nausea and other stomach troubles sometimes associated with endurance running.

During intense exercise, some people experience what's known as "runner's stomach" - the sudden onset of symptoms that can include nausea, cramping and the urgent need to use the toilet. Also known as exercise-induced gastrointestinal syndrome, it seems to affect people regardless of their fitness level.

Previous research suggested that these symptoms may in part ...

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Compression socks may prevent nausea and loose bowels during marathons

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Stomach cramps and the urgent need for the toilet on long runs may partly be caused by decreased blood flow damaging gut cells. Compression socks reduce signs of this damage in marathon runners Wearing compression socks may reduce the intestinal damage thought to cause cramping, nausea and other stomach troubles sometimes associated with endurance running.

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Grace Hartman: Synthetic Embryos in Mouse (Possibly for humans??)

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Grace Hartman: Synthetic Embryos in Mouse (Possibly for humans??)

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I am wondering if synthetic embryos with a basic brain can be grown for mice could this be the start of doing something similar for humans?

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Embryo-like structures grown in an incubator instead of a uterus could lead to better treatments for infertility and a range of other medical conditions

Synthetic embryos made from mouse stem cells have been coaxed into developing the beginnings of a brain and a beating heart while grown in the laboratory.

The result is an embryo-like structure that is the closest yet to a naturally developing embryo in the uterus, says Magdalena Zernicka-Goetz at the University of Cambridge, whose team is also using the same method to make synthetic human embryos, although these are less advanced.

The technique could lead to advances in creating tissues and organs for transplant and one day be used as a fertility treatment for people who cannot make sperm or eggs.

Human embryos can usually only be studied in a dish until they are about a week old because at this stage they normally implant into the placenta, which provides oxygen and nourishment. Also, most countries have a rule that human embryos may not be grown past 14 days, as after that they could be considered separate life forms.

In 2017, Zernicka-Goetz and her team announced they could create embryo-like structures that developed for several days by taking some stem cells from a mouse embryo and growing them alongside trophoblast cells, which normally go on to make the placenta.

The method sparked worldwide interest as it would allow synthetic embryos to be created to order and genetically tweaked to improve our understanding of this mysterious stage of human development. Currently, some unwanted embryos created at IVF clinics may be donated for research, but only small numbers are available and they are often affected by medical conditions. "The big question that we are addressing is how do we start our lives," says Zernicka-Goetz.

Earlier this month, researchers led by Jacob Hanna at the Weizmann Institute of Science in Israel announced they had made synthetic mouse embryos similar to real embryos 8.5 days after fertilisation by growing embryonic stem cells alongside two other kinds of helper cells. These were made by genetically altering embryonic stem cells to turn them into placenta-forming cells as well as a third kind of tissue called the endoderm, which normally directs development.

In the later stages, the structures were cultured in a special rotating incubator with raised oxygen pressure.

Now, Zernicka-Goetz and her team have achieved a similar feat, also using Hanna's incubator, although they sourced the two kinds of helper cells by taking them from other embryos. Their synthetic embryos also resembled real 8.5-day-old embryos. After this stage, the synthetic embryos start to die, but the teams are trying new approaches to help them survive longer.

Zernicka-Goetz says the part that becomes the brain is more advanced than in any previous approaches as it includes the developing forebrain. "This is the very first model system that can develop all parts of the future brain," she says.

Hanna, however, says that his synthetic embryos are similarly advanced as those of Zernicka-Goetz and contain molecules that signify developing forebrain tissue. He says being able to make the synthetic embryos from a single source of embryonic stem cells by genetically manipulating them, as his team did, "is a major surprise, and constitutes a simplified and better method".

If synthetic embryos could be made from human cells, in future they could be used to create new sources of cells and tissues for transplanting into people or healing failing organs, such as the liver or heart. They could also be used to test medicines to see if they are safe for pregnancy, says Zernicka-Goetz.

Lluís Montoliu at the National Centre for Biotechnology in Madrid, Spain, says the creation of synthetic embryos is as important as Dolly the sheep, the first mammal to be made by cloning an adult body cell. "We are undoubtedly facing a new technological revolution, still very inefficient but with enormous potential," he said in a statement.

Journal reference: Nature, DOI: 10.1038/s41586-022-05246-3

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Synthetic mouse embryos with rudimentary brain grown in the lab

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Embryo-like structures grown in an incubator instead of a uterus could lead to better treatments for infertility and a range of other medical conditions Synthetic embryos made from mouse stem cells have been coaxed into developing the beginnings of a brain and a beating heart while grown in the laboratory.

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Heavily processed foods may have the capability of being toxic to ones mental health. Does this ring true?

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Do you love those sugary-sweet beverages, reconstituted meat products and packaged snacks? You may want to reconsider based on a new study that explored whether individuals who consume higher amounts of ultra-processed food have more adverse mental health symptoms.

Although ultra-processed foods are convenient, low cost, quick to prepare or ready-to-eat, these industrial formulations of processed food substances (oils, fats, sugars, starch, protein isolates) contain little or no whole food. They result from extensive 'physical, biological, and chemical processes' that create food products that are deficient in original and natural food. Ultra-processed foods typically include flavorings, colorings, emulsifiers and other cosmetic additives.

While there is some evidence regarding ultra-processed food consumption and depression, data are sparse regarding other adverse mental health symptoms including anxiety and mentally unhealthy days.

Researchers from Florida Atlantic University's Schmidt College of Medicine and collaborators explored a nationally representative sample of the United States population to determine if individuals who consume high amounts of ultra-processed foods report significantly more adverse mental health symptoms including depression, anxiety and mentally unhealthy days.

They measured mild depression, number of mental unhealthy days and number of anxious days in 10,359 adults 18 and older from the U.S. National Health and Nutrition Examination Survey.

Results of the study, published in the journal Public Health Nutrition, showed that individuals who consumed the most ultra-processed foods as compared with those who consumed the least amount had statistically significant increases in the adverse mental health symptoms of mild depression, "mentally unhealthy days" and "anxious days." They also had significantly lower rates of reporting zero "mentally unhealthy days" and zero "anxious days." Findings from this study are generalizable to the entire U.S. as well as other Western countries with similar ultra-processed food intakes.

"The ultra-processing of food depletes its nutritional value and also increases the number of calories, as ultra-processed foods tend to be high in added sugar, saturated fat and salt, while low in protein, fiber, vitamins, minerals and phytochemicals," said Eric Hecht, M.D., Ph.D., corresponding author and an affiliate associate professor in FAU's Schmidt College of Medicine. "More than 70 percent of packaged foods in the U.S. are classified as ultra-processed food and represent about 60 percent of all calories consumed by Americans. Given the magnitude of exposure to and effects of ultra-processed food consumption, our study has significant clinical and public health implications."

Researchers used the NOVA food classification for the study, which is a widely used system recently adopted by the Food and Agricultural Organization of the United Nations. NOVA considers the nature, extent and purpose of food processing in order to categorize foods and beverages into four groups: unprocessed or minimally processed foods, processed culinary ingredients, processed foods and ultra-processed foods.

"Data from this study add important and relevant information to a growing body of evidence concerning the adverse effects of ultra-processed consumption on mental health symptoms," said Charles H. Hennekens, M.D., Dr.PH, co-author, the first Sir Richard Doll Professor of Medicine, and senior academic advisor, FAU Schmidt College of Medicine. "Analytic epidemiologic research is needed to test the many hypotheses formulated from these descriptive data."

According to the National Institute of Mental Health, nearly 1 in 5 adults live with a mental illness. Mental illnesses, including depression and anxiety, are leading causes of morbidity, disability and mortality.

Co-authors of this original research are Anna Rabil, Institute of Etiological Research; Euridice Martinez Steele, Ph.D., University of Sao Paolo; Gary A. Abrams, M.D., University of South Carolina School of Medicine; Deanna Ware, M.P.H., Georgetown University Medical Center and Institute of Etiological Research; and David C. Landy, M.D., Ph.D., University of Kentucky College of Medicine.

This research was funded in part by the Bertarelli Foundation.

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mental health research; nutrition; staying healthy; mental health; depression; nutrition research; food; food and agriculture; agriculture and food

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Feeling anxious or blue? Ultra-processed foods may be to blame

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More than 70 percent of packaged foods in the U.S. are classified as ultra-processed food and represent about 60 percent of all calories consumed by Americans. A study in 10,359 adults 18 and older found those who consumed the most ultra-processed foods as compared with those who consumed the least amount had statistically significant increases in the adverse mental health symptoms of mild depression, 'mentally unhealthy days' and 'anxious days.'

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Growth following trauma is an unspoken actions that tops off the stages of grief. Is this feeling accomplishable by many? or is taking that final step towards easing the pain more difficult to accomplish?

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"What does not kill me, makes me stronger," 19th century German philosopher Friedrich Nietzsche famously wrote. Variations of that aphorism abound in literary, spiritual and, more recently, psychological texts.

That psychological research suggests that at least half of survivors not only recover from traumatic experiences but also go on to develop more appreciation for life, stronger relationships and emotional strength - a phenomenon researchers call "posttraumatic growth."

The idea that bad events can often lead to good outcomes is appealing, especially in this present and difficult moment. More than 6.3 million people worldwide have died from COVID-19, and deaths continue to mount ( SN: 5/18/22). Russia's invasion of Ukraine has surpassed a hundred days ( SN 4/12/22). And a recent string of mass shootings - including at a July 4 parade in Highland Park, Ill., an elementary school in Uvalde, Texas, and a grocery store in Buffalo, N.Y. - has left U.S. communities reeling ( SN: 5/26/22).

But in a series of talks presented in May in Chicago at the Association for Psychological Science conference, some researchers called findings of posttraumatic growth "largely illusory." Growth studies suffer from serious methodological flaws, these researchers say. That includes a reliance on surveys that require people to assess their personal growth over time, a task that most people struggle with.

Better research tools may not remedy the problem. That's because these studies are fundamentally flawed, the researchers say. They argue that the impetus to study trauma in terms of growth stems from a Western mind-set that tends to value positive emotions and devalue or even avoid negative emotions ( SN: 12/7/19). That can pressure survivors to deny or suppress their negative feelings, which could have harmful consequences.

That yearning for positive outcomes can create "toxic cultural narratives," says personality psychologist Eranda Jayawickreme of Wake Forest University in Winston-Salem, N.C. Referring to parents who lost a child in the Uvalde mass shooting, he says: "There is something grotesque about this expectation that people could come back from something like this."

Focusing on the good

A half-century ago, psychologists largely treated a person's difficulty in rebounding from traumatic events as a personal failing. But research on returning Vietnam War veterans and other trauma survivors began shifting that way of thinking. In 1980, the American Psychiatric Association created a category for posttraumatic stress disorder, or PTSD, in its manual of mental disorders. Those struggling with the disorder might experience flashbacks, nightmares and severe anxiety.

"Thirty years ago, everyone was focused on the worst outcomes," says trauma and resilience expert George Bonanno of Columbia University.

But only about one-fifth of people who experience trauma develop PTSD, psychologists realized. In the mid-1990s, psychologists Richard Tedeschi and Lawrence Calhoun, both then at the University of North Carolina at Charlotte, wrote in the 1996 Journal of Traumatic Stress that a focus on suffering obscured the good that can emerge from trauma.

The pair developed a now widely used "growth inventory" to assess positive outcomes that people reported after experiencing a traumatic event. In the 21-item survey, respondents rate statements such as "I have more compassion for others" and "I established a new path for my life." Respondents can choose from a score of 0 for "I did not experience this change as a result of my crisis" to 5 for "I experienced this change to a very great degree as a result of my crisis." The items reflect five broad categories: relating to others, personal strength, new possibilities, appreciation of life and spiritual change.

"Posttraumatic growth is you go down to the depths and then at some later point, rise above that baseline into some other realm," says Tedeschi, now the chair of Boulder Crest Institute for Posttraumatic Growth, an organization in Bluemont, Va., that uses research on posttraumatic growth to help combat veterans, first responders and their families.

Cracks in the theory

But some researchers soon began to question people's ability to accurately respond to the growth survey.

In a now-seminal 2009 study in Psychological Science, researchers recruited about 1,500 undergraduate students and tracked them for eight weeks. Once at the start of the study and once at the end, students responded to surveys for each of the five growth categories covered by the growth inventory, along with a modified version of the inventory.

Unlike Tedeschi and Calhoun's inventory, which asks respondents to compare their present state of mind to the past, the five surveys and modified inventory asked respondents to reflect on the present. For instance, in the relationship quality category, respondents rated the statement: "I enjoy personal and mutual conversations with family members or friends."

During that eight-week period, 122 students reported experiencing a traumatic event that caused high levels of distress. Those students also completed the standard growth inventory at the end of the eight weeks. The researchers found no correlation between high perceived growth scores on the standard inventory and actual growth scores on the modified inventory and five surveys related to well-being.

That mismatch occurs because people are terrible at remembering how they felt in the past, says study coauthor Crystal Park, a clinical health psychologist at the University of Connecticut in Storrs. "I want to throw out the concept of people being able to accurately report that they have grown."

Tedeschi counters that trauma cleaves one's life into a before and after, making it more feasible for many people to distinguish changes over time. What's more, growth takes time, he says. "You can't expect people to change their spiritual beliefs in eight weeks."

But how much time? And if enough time passes, how does one know that the growth arises from the trauma and not some other major life experience, like moving across the country or having children? Research shows that people are not great at introspection, Jayawickreme says. "We tend to come up with all types of stories for change, but those stories are just stories. They don't really reflect what actually caused that change."

'Pulling for growth'

Other problems come with the design of the original inventory, Jayawickreme and others argue. For example, the questions account for positive changes only, and the worst or lowest outcome a respondent can give is that they experienced no change as a result of their crisis. That framing puts pressure on survivors to report growth when they may feel worse, Jayawickreme says. "The items are pulling for growth."

Tedeschi and colleagues have recently developed a new growth survey that also accounts for negative changes following trauma. But it's not yet as widely used in research on posttraumatic growth as the original.

Meanwhile, in unpublished work, trauma researcher Adriel Boals of the University of North Texas in Denton sought to overcome what he sees as the original survey's growth bias in a different way. He asked people whether they changed because of a traumatic event, a measure of growth, or despite the event.

"Half the people are picking, 'I changed despite this event,'" Boals says. That suggests that people who may report growth on the original inventory do not actually attribute that growth to the trauma but to other life experiences.

What's more, say Jayawickreme and others, unlike most psychological surveys, which require respondents to complete a single cognitive task along the lines of "how are you doing now" or "reflect on the present," the original growth inventory requires four cognitive tasks. Respondents must consider how they are doing at the moment and how they were doing prior to the trauma. They then must compute that difference in well-being, as well as determine if the trauma, or some other life event such as aging or having a child, caused the change.

But people don't actually go through those steps. That finding was reported in March in Anxiety, Stress and Coping and at the May conference by Boals, Park and Elizabeth Griffith, a psychologist also at the University of North Texas.

When the team compared response times among college students taking the standard growth inventory with students taking a simplified version involving a single cognitive task, the researchers found that the students completing the standard inventory took just 8 percent longer than the other students. That equates to just a half-second longer response time per item, Boals says. "If you can go through steps 2, 3 and 4 ... in half a second, you're drinking stronger coffee than I am."

Avoiding negative emotions

Beyond the methodological particulars, some researchers studying trauma across cultures question some Western psychologists' focus on personal growth and, to a lesser degree, resilience - a phenomenon marked by stability during hard times, rather than a steep increase in well-being after an initial decline as observed in posttraumatic growth ( SN: 10/19/14).

"In Euro-American societies, 'resilience' and 'posttraumatic growth' are commonly used metaphorical terms for positive responses to extreme adversity," write University of Zurich psychologists Iara Meili and Andreas Maercker in 2019 in Transcultural Psychiatry. They attribute the popularity of these Western "metaphors" to individualistic societies' emphasis on self-determination and agency, even in the face of illness or death. These concepts exist elsewhere, Maercker says. But they rarely take on such outsize significance - what he calls "almost a religious approach."

A societal expectation of growth can put tremendous pressure on survivors to hide their suffering, Jayawickreme says.

Take, for instance, a study where researchers compared outcomes among about 380 Norwegian soldiers who deployed to Iraq in 2004. Soldiers who reported the most personal growth five months after returning home also reported the most posttraumatic stress symptoms 10 months later, researchers noted in 2015 in Clinical Psychological Science.

"Self-reports of posttraumatic growth should be highly correlated with doing well on other measurements, like less depression, more satisfaction with life, those types of things," says Boals, who was not involved with this research. "But if anything, [growth] is positively correlated with PTSD symptoms."

Ultimately, the most compassionate response to suffering is to validate survivors' feelings, Jayawickreme says. "How people respond to adversity is nuanced. People can change in positive ways. People can change in negative ways. People cannot change at all. And that's fine."

Questions or comments on this article? E-mail us at feedback@sciencenews.org | Reprints FAQ

Citations

R.G. Tedeschi and L.G. Calhoun. The posttraumatic growth inventory: Measuring the positive legacy of trauma. Journal of Traumatic Stress. Vol. 9, 1996, p. 455. doi: 10.1002/jts.2490090305.

A. Boals, E.L. Griffith and C.L. Park. Can respondents accurately report posttraumatic growth when coached through the required cognitive steps? Anxiety, Stress and Coping.Posted online March 10, 2022. doi: 10.1080/10615806.2022.2047949.

I. Meili and A. Maercker. Cultural responses on positive responses to extreme adversity: A playing field for metaphors. Transcultural Psychiatry.Vol. 56, October 2019, p. 807. doi: 10.1177/1363461519844355.

K. Taku et al. Posttraumatic growth (PTG) and posttraumatic depreciation (PTD) across ten countries: Global validation of the PTG-PTD theoretical model. Personality and Individual Differences, Vol. 169, February 2021, p. 110222. doi:10.1016/j.paid.2020.110222.

I.M. Englehard, M.J.J. Lommen and M. Sijbrandig. Changing for better or worse? Posttraumatic growth reported by soldiers deployed to Iraq. Clinical Psychological Science.Vol. 3, September 2015, p. 663. doi: 10.1177/2167702614549800.

P. Frazier et al. Does self-reported posttraumatic growth reflect genuine positive change? Psychological Science.Vol. 20, July 1, 2009, p. 912. doi: 10.1111/j.1467-9280.2009.02381.x.

Sujata Gupta is the social sciences writer and is based in Burlington, Vt.

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The idea that many people grow following trauma may be a myth

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Studies of posttraumatic growth are fundamentally flawed and can contribute to toxic cultural narratives, researchers say.

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Aliya Arous: human evolution through climate change

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Aliya Arous: human evolution through climate change

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This article explains how climate change could have affected the course of human evolution. I wonder how it shaped humans for the better and for the worse?

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Recurring climate changes may have orchestrated where Homo species lived over the last 2 million years and how humankind evolved.

Ups and downs in temperature, rainfall and plant growth promoted ancient hominid migrations within and out of Africa that fostered an ability to survive in unfamiliar environments, say climate physicist and oceanographer Axel Timmermann and colleagues. Based on how the timing of ancient climate variations matched up with the comings and goings of different fossil Homo species, the researchers generated a novel - and controversial - outline of human evolution. Timmermann, of Pusan National University in Busan, South Korea, and his team present that scenario April 13 in Nature.

Here's how these scientists tell the story of humankind, starting roughly 2 million years ago. By that time, Homo erectus had already begun to roam outside Africa, while an East African species called H. ergaster stuck close to its home region. H. ergaster probably evolved into a disputed East African species called H. heidelbergensis, which split into southern and northern branches between 850,000 and 600,000 years ago. These migrations coincided with warmer, survival-enhancing climate shifts that occur every 20,000 to 100,000 years due to variations in Earth's orbit and tilt that modify how much sunlight reaches the planet.

Then, after traveling north to Eurasia, H. heidelbergensis possibly gave rise to Denisovans around 430,000 years ago, the researchers say. And in central Europe, harsh habitats created by recurring ice ages spurred the evolution of H. heidelbergensis into Neandertals between 400,000 and 300,000 years ago. Finally, in southern Africa between 310,000 and 200,000 years ago, increasingly harsh environmental conditions accompanied a transition from H. heidelbergensis to H. sapiens, who later moved out of Africa.

But some researchers contend that H. heidelbergensis, as defined by its advocates, contains too many hard-to-categorize fossils to qualify as a species.

An alternative view to the newly proposed scenario suggests that, during the time that H. heidelbergensis allegedly lived, closely related Homo populations periodically split up, reorganized and bred with outsiders, without necessarily operating as distinct biological species (SN: 12/13/21). In this view, mating among H. sapiens groups across Africa starting as early as 500,000 years ago eventually produced a physical makeup typical of people today. If so, that would undermine the validity of a neatly branching evolutionary tree of Homo species leading up to H. sapiens, as proposed by Timmermann's group.

The new scenario derives from a computer simulation of the probable climate over the last 2 million years, in 1,000-year intervals, across Africa, Asia and Europe. The researchers then examined the relationship between simulated predictions of what ancient habitats were like in those regions and the dates of known hominid fossil and archaeological sites. Those sites range in age from around 2 million to 30,000 years old.

Previous fossil evidence indicates that H. erectus spread as far as East Asia and Java ( SN: 12/18/19). Timmermann's climate simulations suggest that H. erectus, as well as H. heidelbergensis and H. sapiens, adapted to increasingly diverse habitats during extended travels. Those migrations stimulated brain growth and cultural innovations that "may have made [all three species] the global wanderers that they were," Timmermann says.

The new habitat simulations also indicate that H. sapiens was particularly good at adjusting to hot, dry regions, such as northeastern Africa and the Arabian Peninsula.

Climate, habitat and fossil data weren't sufficient to include additional proposed Homo species in the new evolutionary model, including H. floresiensis in Indonesia ( SN: 3/30/16) and naledi in South Africa ( SN: 5/9/17).

It has proven difficult to show more definitively that ancient environmental changes caused transitions in hominid evolution. For instance, a previous proposal that abrupt climate shifts resulted in rainy, resource-rich stretches of southern Africa's coast, creating conditions where H. sapiens then evolved ( SN: 3/31/21), still lacks sufficient climate, fossil and other archaeological evidence.

Paleoanthropologist Rick Potts of the Smithsonian Institution in Washington, D.C., has developed another influential theory about how climate fluctuations influenced human evolution that's still open to debate. A series of climate-driven booms and busts in resource availability, starting around 400,000 years ago in East Africa, resulted in H. sapiens evolving as a species with a keen ability to survive in unpredictably shifting environments, Potts argues ( SN: 10/21/20). But the new model indicates that ancient H. sapiens often migrated into novel but relatively stable environments, Timmermann says, undermining support for Potts' hypothesis, known as variability selection.

The new findings need to be compared with long-term environmental records at several well-studied fossil sites in Africa and East Asia before rendering a verdict on variability selection, Potts says.

The new model "provides a great framework" to evaluate ideas such as variability selection, says paleoclimatologist Rachel Lupien of Lamont-Doherty Earth Observatory in Palisades, N.Y. That's especially true, Lupien says, if researchers can specify whether climate and ecosystem changes that played out over tens or hundreds of years were closely linked to ancient Homo migrations.

For now, much remains obscured on the ancient landscape of human evolution.

Questions or comments on this article? E-mail us at feedback@sciencenews.org | Reprints FAQ

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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How ancient, recurring climate changes may have shaped human evolution

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Climate changes drove where Homo species lived over the last 2 million years, with a disputed ancestor giving rise to H. sapiens, a new study claims.

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We know that identical twins do share the same DNA but it is interesting to see how they could share the same chemical markers.

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Identical siblings are used to sharing a lot with their twin, including their DNA. But new research suggests all identical twins share a common signature of twinhood, not in their DNA, but on it.

This signature is part of the epigenome, chemical markers that dot many spots along DNA and influence the activity of genes without altering their sequence. Identical twins everywhere largely share a specific set of these marks that persists from birth to adulthood, researchers report September 28 in Nature Communications. These shared epigenetic tags could be used to identify people who were conceived as identical twins but lost their sibling in the womb or were separated at birth.

"This paper is absolutely fascinating," says Nancy Segal, a developmental psychologist at California State University, Fullerton who has researched twins but wasn't involved in the study. The research sets the groundwork for scientists to better understand "what might cause a fertilized egg to split and form monozygotic [identical] twins," she says.

Despite humans' age-old fascination with identical twins, the biological process that generates them, known as monozygotic twinning, "is an enigma," says Jenny van Dongen, an epigeneticist at Vrije Universiteit Amsterdam.

Researchers know that identical twins form after a fertilized egg, called a zygote, somehow splits into two embryos during development. But why this cleavage happens remains unknown, van Dongen says. For the most part, identical twins don't run in families, and they occur at roughly the same rate worldwide - about 3 to 4 per 1,000 births. With no clear genetic or environmental cause, the prevailing hypothesis is that identical twins arise at random, she says.

Early development, for twins and non-twins alike, happens amid a flurry of epigenetic changes that turn many genes on or off as an embryo takes shape. Some of these changes may account for slight differences between identical twins ( SN: 7/17/12). So to better understand what makes a zygote split to form identical twins, "it makes sense to look at epigenetics," van Dongen says.

She and colleagues looked for epigenetic differences at over 450,000 sites along the genomes of nearly 6,000 monozygotic twins and dizygotic, or fraternal, twins. Comparing identical twins with fraternal twins, as opposed to comparing twins to non-twins, allowed the researchers to rule out any epigenetic changes that stemmed from the unusual experience of sharing a womb.

At 834 spots along the genome, identical twins were strikingly similar, the researchers found. These shared epigenetic marks were concentrated in certain parts of the genome, including centromere and telomere regions on chromosomes. Some marks were near genes involved in early developmental processes, including those that regulate how tightly cells stick to one another. Whether these differences have health consequences for identical twins is unclear, van Dongen says.

These epigenetic signs popped up in twins young and old, from places as far-flung as Finland to Australia and were found in different cell types. The shared marks are so uniquely common to identical twins that the researchers were able to devise a test that can determine, with up to 80 percent accuracy, whether an individual is an identical twin. That includes individuals who don't know that they lost their twin during pregnancy, a phenomenon known as vanishing twin syndrome, and twins who were separated at birth.

"This is a very, very important finding that opens up a lot of avenues of inquiry," says Segal, the developmental psychologist. For example, identical twins are predisposed for a variety of conditions, from left-handedness to certain congenital disorders such as spina bifida, where the spine fails to develop properly. Perhaps, for some portion of people, these conditions stem from being an unknown identical twin, she says.

Whether this epigenetic signature is a cause, consequence or by-product of monozygotic twinning remains unclear, van Dongen says. It's possible that some of these epigenetic changes tell a zygote to split. Alternatively, these chemical marks could reflect the epigenetic aftermath of the splitting event.

"They could be like a persistent molecular scar of the [splitting] process itself," says Robert Waterland, an epigeneticist at Baylor College of Medicine in Houston. "An embryo splitting in two pieces would kind of upset things," he says, and that could disrupt normal epigenetic processes in a way that leaves a permanent mark. He gravitates towards that molecular scar interpretation, though more studies are needed to know for sure, he says.

Questions or comments on this article? E-mail us at feedback@sciencenews.org

A version of this article appears in the November 6, 2021 issue of Science News.

Jonathan Lambert is a former staff writer for biological sciences, covering everything from the origin of species to microbial ecology. He has a master's degree in evolutionary biology from Cornell University.

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All identical twins may share a common set of chemical markers on their DNA

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Identical siblings are used to sharing a lot with their twin, including their DNA. But new research suggests all identical twins share a common signature of twinhood, not in their DNA, but on it. This signature is part of the epigenome, chemical markers that dot many spots along DNA and influence the activity of genes without altering their sequence.

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The Younger Dryas Impact Theory hypothesizes that a comet strike around 12,000 years ago caused a melting of the northern glacial sheet. Could this theory explain the loss of megafauna and decline in human populations around this time period?

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An interdisciplinary team of scientists from seven U.S. institutions says a disregard of three critical protocols, including sorting samples by size, explains why a group challenging the theory of a North American meteor-impact event some 12,900 years ago failed to find iron- and silica-rich magnetic particles in the sites they investigated.

Not separating samples of the materials into like-sized groupings made for an avoidable layer of difficulty, said co-author Edward K. Vogel, a professor of psychology at the University of Oregon.

The new independent analysis -- published this week in the online Early Edition of the Proceedings of the National Academy of Sciences -- did, in fact, isolate large quantities of the "microspherules" at the involved sites where the challengers previously reported none. Lead author Malcolm A. LeCompte, an astrophysicist at Elizabeth City State University in North Carolina, said the findings support the climate-altering cosmic impact, but his team stopped short of declaring this as proof of the event.

The Clovis-age cosmic-impact theory was proposed in 2007 by a 26-member team led by Richard B. Firestone. That team included University of Oregon archaeologists Douglas J. Kennett and Jon M. Erlandson. While other groups have found corroborating evidence of a potential cosmic event, other groups reported difficulties doing so. One group, led by Todd A Surovell of the University of Wyoming, did not find any microspherule evidence at five of seven sites they tested, including two previously studied locations where Firestone reported large numbers of microspherules.

"In investigating the two common sites and a third tested only by Surovell's team, we found spherules in equal or greater abundance than did the Firestone team, and the reported enhancement was in strata dated to about 13,000 years before the present," LeCompte said. "What we've done is provide evidence that is consistent with an impact, but we don't think it proves the impact. We think there's a mystery contained in the Younger Dryas strata, and that we've provided some validation to the original research by Firestone's group."

The particles in question, the team concluded, are terrestrial as was claimed by the Firestone group, and not of meteoric origin as claimed by other challengers including Surovell's group, and are similar to metamorphic material in Earth's crust. That determination was made using electron microscopy and spectroscopy.

"These spherules have evidence of very high-temperature melting and very rapid cooling, which is characteristic of debris ejected from an impact," LeCompte said. Speherules would have melted at temperatures approaching 2,000 degrees Celsius (more than 3,000 degrees Fahrenheit), he added. Cosmic materials, including the some microspherules, regularly fall to earth from space due to meteorite ablation, but the spherules found in soils dating to 13,000 years ago are much different, he added. Other researchers had suggested that these spherules were deposited by a cosmic rain or resulted through slow, terrestrial processes occurring under ambient conditions.

LeCompte and some key collaborators wondered why Surovell didn't find any spherules, and that led them to Vogel. Many of the spherules investigated were tiny, ranging in size from 20 to 50 micrometers (microns); about the diameter of a human hair.

"The inherent difficulty in finding these small, relatively rare magnetic microspherules suggested there may be inherent limitations in human faculties that needed to be addressed, and that's how and why we sought out UO Professor Ed Vogel. His research into human cognitive capabilities proved so important in understanding both why the search was so difficult and why size-sorting was effective and important in making it easier," LeCompte said.

Vogel specializes in the ability of people to find specific items amid multiple distractions.

"A visual search is a very error-prone process," Vogel said. "This was a case of looking at millions of particles from which you are hoping to find something that might be present much less than 0.1 percent of the time." Size-sorting, he said, is vital because it is easier to find a target item with a characteristic shape and color when all of the many more-distracting objects are very similar. "It is a slow, tedious process to examine such quantities of materials with the human eyes when object sizes are extremely dissimilar."

"Science is only as good as the humans who conduct it, and this study shows how the minds of researchers can operate in some surprising ways," said Kimberly Andrews Espy, UO vice president for research and innovation, and dean of the graduate school. "Dr. Vogel's excellent work, which illustrates the importance of understanding how the human mind processes information and the consequences it can have beyond making everyday computations, reflects the University of Oregon's strengths in interdisciplinary research."

LeCompte described Surovell's study "as possibly the most damning of the reports that had challenged the original theory."

"Todd had worked very hard and couldn't find the spherules, but I think he made some fatal errors that need to be pointed out," LeCompte said. "It is instructive in that we initially made the same mistake and came to the same erroneous conclusion, but then we corrected our mistake. I would say this is a case of a missed opportunity due to their deviations from the protocol."

Two other critical protocol deviations not followed by the challengers involved the amounts of material examined and the use of microscopy techniques specified in Firestone's original research. Another two minor aspects of the protocol also were not repeated, reported LeCompte's team, which, in addition to Vogel, included an archaeologist, two materials scientists, a botanist, a periglacial geographer and an aerospace engineer.

LeCompte's team -- using the protocols of Firestone's group and electron microscopy -- additionally studied a quarry site in Topper, S.C., where Clovis-age people had made stone tools. After removing chert debris associated with tool making in soil at the depth of the Clovis occupation, LeCompte said, researchers observed virtually no spherules below it, while in soil just above the chert fragments they found a spike in the number of telltale spherules.

Further above that level, he noted, the soil layers were essentially "a dead zone" somewhat analogous to the K-T boundary, or "tombstone layer," from an extinction event that occurred 65 million years ago. At Topper, the dead zone showed almost no trace of human habitation for perhaps as long as 1,000 years duration.

"This suggests that something very dramatic happened," LeCompte said.

"The effects of such an impact would have been catastrophic on a global scale," said co-author Barrett Rock, a botanist at the University of New Hampshire. "On the order of 36 ice-age species became extinct, and the Clovis human culture eventually lost. All of this in response to dramatic changes in the vegetation at the base of the faunal food chain."

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comets and meteors; cosmic rays; sun; near-earth object impacts; global warming; atmosphere; cultures; origin of life; human evolution

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Challengers to Clovis-age impact theory missed key protocols, new study finds

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An interdisciplinary team of scientists from seven US institutions says a disregard of three critical protocols, including sorting samples by size, explains why a group challenging the theory of a North American meteor-impact event some 12,900 years ago failed to find iron- and silica-rich magnetic particles in the sites they investigated.

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What affect did human migration on the evolution of humankind and expansion of civilization?

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The Five-Million-Year Odyssey
Peter Bellwood
Princeton Univ., $29.95
Archaeologist Peter Bellwood's academic odyssey wended from England to teaching posts halfway around the world, first in New Zealand and then in Australia. For more than 50 years, he has studied how humans settled islands from Southeast Asia to Polynesia.

So it's fitting that his new book, a plain-English summary of what's known and what's not about the evolution of humans and our ancestors, emphasizes movement. In The Five-Million-Year Odyssey, Bellwood examines a parade of species in the human evolutionary family - he collectively refers to them as hominins, whereas some others (including Science News) use the term hominids ( SN: 9/15/21) - and tracks their migrations across land and sea. He marshals evidence indicating that hominids in motion continually shifted the direction of biological and cultural evolution.

Throughout his tour, Bellwood presents his own take on contested topics. But when available evidence leaves a debate unresolved, he says so. Consider the earliest hominids. Species from at least 4.4 million years ago or more whose hominid status is controversial, such as Ardipithecus ramidus, get a brief mention. Bellwood renders no verdict on whether those finds come from early hominids or ancient apes. He focuses instead on African australopithecines, a set of upright but partly apelike species thought to have included populations that evolved into members of our own genus, Homo, around 2.5 million to 3 million years ago. Bellwood hammers home the point that stone-tool making by the last australopithecines, the first Homo groups or both contributed to the evolution of bigger brains in our ancestors.

The action speeds up when Homo erectus becomes the first known hominid to leave Africa, roughly 2 million years ago. Questions remain, Bellwood writes, about how many such migrations occurred and whether this humanlike species reached distant islands such as Flores in Indonesia, perhaps giving rise to small hominids called hobbits, or Homo floresiensis ( SN: 3/30/16). What's clear is that H. erectus groups journeyed across mainland Asia and at least as far as the Indonesian island of Java.

Intercontinental migrations flourished after Homo sapiens debuted, around 300,000 years ago in Africa. Bellwood regards H. sapiens, Neandertals and Denisovans as distinct species that interbred in certain parts of Asia and Europe. He suggests that Neandertals disappeared around 40,000 years ago as they mated with members of more numerous H. sapiens populations, leaving a genetic legacy in people today. But he does not address an opposing argument that different Homo populations at this time, including Neandertals, were too closely related to have been separate species and that it was intermittent mating among these mobile groups that drove the evolution of present-day humans ( SN: 6/5/21).

Bellwood gives considerable attention to the rise of food production and domestication in Europe and Asia after around 9,000 years ago. He builds on an argument, derived from his 2004 book First Farmers, that expanding populations of early cultivators migrated to new lands in such great numbers that they spread major language families with them. For instance, farmers in what's now Turkey spread Indo-European languages into much of Europe sometime after roughly 8,000 years ago, Bellwood contends.

He rejects a recent alternative proposal, based on ancient DNA evidence, that horse-riding herders of Central Asia's Yamnaya culture brought their traditions and Indo-European tongues to Europe around 5,000 years ago ( SN: 11/15/17). Too few Yamnaya immigrated to impose a new language on European communities, Bellwood says. Similarly, he argues, ancient Eurasian conquerors, from Alexander the Great to Roman emperors, couldn't get speakers of regional languages to adopt new ones spoken by their outnumbered military masters.

Bellwood rounds out his evolutionary odyssey with a reconstruction of how early agricultural populations expanded through East Asia and beyond, to Australia, a string of Pacific islands and the Americas. Between about 4,000 and 750 years ago, for instance, sea-faring farmers spread Austronesian languages from southern China and Taiwan to Madagascar in the west and Polynesia in the east. Precisely how they accomplished that remarkable feat remains a puzzle.

Disappointingly, Bellwood doesn't weigh in on a recent archaeological argument that ancient societies were more flexible and complex than long assumed ( SN: 11/9/21). On the plus side, his evolutionary odyssey moves along at a brisk pace and, like our ancestors, covers a lot of ground.

Buy The Five-Million-Year Odyssey from Bookshop.org. Science News is a Bookshop.org affiliate and will earn a commission on purchases made from links in this article.

Questions or comments on this article? E-mail us at feedback@sciencenews.org | Reprints FAQ

A version of this article appears in the August 27, 2022 issue of Science News.

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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'The Five-Million-Year Odyssey' reveals how migration shaped humankind

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A globe-trotting trek through history shows how past population migrations changed the course of human biology and culture.

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This article talks about experiments done with artificial sugars that contain zero calories. Zero calorie artificial sugar has been used for a while now and studies are still being conducted on wether it is safe or not. Is it better to gain weight or increase your gut bacteria?

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As Diet Coke and its sweetener aspartame wrap up 40 years or so on American store shelves, the decades-long controversy around the safety of sugar substitutes continues. Ever since diet drinks hit the stores in the 1950s, rumors have swirled that such sweeteners-which today also include saccharin, sucralose and stevia-do more than satisfy a sweet tooth without the calories of sugar. But whether that "more" exists hasn't been easy to establish.

In a new study of four sugar substitutes, researchers found that these nonnutritive sweeteners don't just travel through the body unnoticed. The study results, published on August 19 in Cell, link two of the sweeteners-saccharin and sucralose-to spikes in glucose levels and suggest all four are tied to a shift in gut microbe profiles. Whether these findings translate into trouble, benefit or neither remains to be seen, and aficionados of diet drinks don't need to trash the diet soda can just yet.

"It's cool science and was very well designed, thought out and executed," says Dylan Mackay, an assistant professor of nutrition and chronic disease at the University of Manitoba, who was not involved in the study. "I've always wanted to do these more at-home trials, and they were able to pull it off in a really interesting way."

In 2014 researchers found a link between microbiome changes and blood glucose responses in mice after intake of sugar substitutes. To see if those same links applied to humans in the new study, the scientists selected participants from a potential pool of more than 1,375people, ruling out anyone who consumed noncaloric sweeteners in their regular daily life. Some had unknowingly done so by way of protein powders, chewing gum, or low-sugar snacks or desserts.

The researchers split the final 120 participants into six groups of 20. In four of these groups, participants consumed commercial packets of one of the four sweeteners at levels below their federal daily limit. A fifth group consumed only the filler used in these packets, which is commonly added to bulk out the tiny amount of sugar substitute they contain. The sixth group had no intervention.

During the two weeks that participants consumed their assigned sweetener or the filler, they also took oral glucose tolerance tests, which are used to measure the body's response to sugar and can be employed to diagnose some forms of diabetes. For these tests, they drank a glucose solution every morning after overnight fasting and used home-based continuous glucose monitors to track their blood glucose levels. The researchers also collected oral and stool samples from the participants to analyze the species of microbes they hosted. Study investigators additionally measured levels of some products of metabolism in the blood.

The participants who consumed saccharin or sucralose had a steeper blood glucose response than any of the other groups. When participants consumed any of the four sugar substitutes, their gut bacteria profile changed during the two weeks of intake. Along with these changes, levels of the metabolic products changed, too. For example, in participants who took saccharin, the production of a type of amino acid increased,echoing patterns seen in people with diabetes.

To confirm a link between microbial profiles and blood glucose responses, the investigators orally administered microbiomes-taken from the human participants with the highest and lowest blood glucose spikes following sweetener consumption-to germ-free mice. Mice exposed to microbiomes from human "top responders" showed changes in their blood glucose that "very significantly mirrored those of the donor individuals," says study author Eran Elinav, principal investigator of the Host-Microbiome Interaction Research Group at the Weizmann Institute of Science in Rehovot, Israel, and director of the Microbiome and Cancer Division at the German National Cancer Center in Heidelberg.

This part of the work "is a really cool portion of the paper," Mackay says. The findings in mice "are interesting mechanistic evidence that maybe [these sweeteners] are having an effect."

The effects of the sweeteners on blood glucose are likely highly personalized, Elinav says. But the results suggest these compounds don't just pass through the body, as some originally thought.

Part of the personalized response will relate to the health of the person involved, Mackay says. The findings "can't extend to people who may be overweight or have obesity or impaired glucose tolerance or type 1 or type 2 diabetes," he says.

The findings don't settle the question of whether any effects will be meaningful for human health-a subject to tackle in other studies, Elinav says. The researchers also don't know if these effects will persist beyond the two weeks of exposure in the current study, Mackay says.

The study involved healthy people without overweight or obesity and who represent only a subset of the population that consumes food and drink with these sugar substitutes, Mackay notes. "From a user perspective, as someone with type 1 diabetes, almost everything I use has aspartame," he says. "I'm not going to stop that and switch back to regular glucose or sugar-containing products because of these results."

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Some Sugar Substitutes Affect Blood Glucose and Gut Bacteria

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As Diet Coke and its sweetener aspartame wrap up 40 years or so on American store shelves, the decades-long controversy around the safety of sugar substitutes continues. Ever since diet drinks hit the stores in the 1950s, rumors have swirled that such sweeteners-which today also include saccharin, sucralose and stevia-do more than satisfy a sweet tooth without the calories of sugar.

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Mosquitos attraction to humans (Trisha Gite) 

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Mosquitos attraction to humans (Trisha Gite) 

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This article talks about how scientists are trying to break the attraction of Mosquitos to humans. The research is cutting the receptors of Mosquitos that causes the attraction to get stronger. Will cutting off these receptors and researching further into the Mosquitos "Brain" really stop their attraction to us, human's blood?

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When female mosquitoes are looking for a human to bite, they smell a unique cocktail of body odors that we emit into the air. These odors then stimulate receptors in the mosquitoes' antenna. Scientists have tried deleting these receptors in attempts to make humans undetectable to mosquitoes.

However, even after knocking out an entire family of odor-sensing receptors from the mosquito genome, mosquitoes still find a way to bite us. Now, a group of researchers, publishing in the journal Cell on August 18, found that mosquitoes have evolved redundant fail-safes in their olfactory system that make sure they can always smell our scents.

"Mosquitoes are breaking all of our favorite rules of how animals smell things," says Margo Herre, a scientist at Rockefeller University and one of the lead authors of the paper.

In most animals, an olfactory neuron is only responsible for detecting one type of odor. "If you're a human and you lose a single odorant receptor, all of the neurons that express that receptor will lose the ability to smell that smell," says Leslie Vosshall of the Howard Hughes Medical Institute and a professor at Rockefeller University and the senior author of the paper. But she and her colleagues found that this is not the case in mosquitoes.

"You need to work harder to break mosquitoes because getting rid of a single receptor has no effect," says Vosshall. "Any future attempts to control mosquitoes by repellents or anything else has to take into account how unbreakable their attraction is to us."

"This project really started unexpectedly when we were looking at how human odor was encoded in the mosquito brain," says Meg Younger, a professor at Boston University and one of the lead authors of the paper.

They found that neurons stimulated by the human odor 1-octen-3-ol are also stimulated by amines, another type of chemical mosquitoes use to look for humans. This is unusual since according to all existing rules of how animals smell, neurons encode odor with narrow specificity, suggesting that 1-octen-3-ol neurons should not detect amines.

"Surprisingly, the neurons for detecting humans through 1-octen-3-ol and amine receptors were not separate populations," says Younger. This may allow all human-related odors to activate "the human-detecting part" of the mosquito brain even if some of the receptors are lost, acting as a fail-safe.

The team also utilized single-nucleus RNA sequencing to see what other receptors individual mosquito olfactory neurons are expressing. "The result gave us a broad view of just how common co-expression of receptors is in mosquitoes," says Olivia Goldman, another lead author of the paper.

Vosshall thinks that other insects may have a similar mechanism. Christopher Potter's research group at Johns Hopkins University recently reported that fruit flies have similar co-expression of receptors in their neurons. "This may be a general strategy for insects that depend heavily on their sense of smell," says Vosshall.

In the future, Meg Younger's group plans to uncover the functional significance of the co-expression of different types of olfactory receptors.

This work was partially supported by the U.S. National Institute of Health.

Journal Reference:

Margaret Herre, Olivia V. Goldman, Tzu-Chiao Lu, Gabriela Caballero-Vidal, Yanyan Qi, Zachary N. Gilbert, Zhongyan Gong, Takeshi Morita, Saher Rahiel, Majid Ghaninia, Rickard Ignell, Benjamin J. Matthews, Hongjie Li, Leslie B. Vosshall, Meg A. Younger. Non-canonical odor coding in the mosquito. Cell, 2022; 185 (17): 3104 DOI: 10.1016/j.cell.2022.07.024

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nervous system; human biology; workplace health; personalized medicine; insects (including butterflies); dogs; nature; biology

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Mosquitoes have neuronal fail-safes to make sure they can always smell humans

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When female mosquitoes are looking for a human to bite, they smell a unique cocktail of body odors that we emit into the air. These odors then stimulate receptors in the mosquitoes' antenna. Scientists have tried deleting these receptors in attempts to make humans undetectable to mosquitoes.

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Evan Hunt: Artificial blood could slow organ decay after death

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Evan Hunt: Artificial blood could slow organ decay after death

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Use of an artificial blood substitute can reverse cell damage caused by lack of oxygen and could make more organs available for transplants, treat heart attacks and strokes and even reverse death

A procedure that reverses cell damage after the heart has stopped pumping blood may lead to more organ transplants and better treatments for heart attacks and strokes, and one day could even save the lives of people who would currently be considered dead.

The method, which so far has been tested on pigs, involves connecting an animal to a pump that perfuses their bodies with an artificial blood substitute containing oxygen and a mixture of other chemicals to prevent cell death and promote repair processes.

"We have shown that cells don't die as quickly as we assumed they do, which opens up possibilities for intervention. We can persuade cells not to die," says Zvonimir Vrselja at Yale School of Medicine.

Currently, people whose hearts are failing may be connected to heart-lung machines, which oxygenate their blood, remove carbon dioxide from it and pump it around the body.

But if someone's heart stops while they are outside of a hospital, their cells and organs are quickly damaged by the lack of oxygen and their chances of survival plummet. Their blood becomes more acidic from a build-up of CO2 and many damaging substances are released. "The blood is full of all sorts of bad things," says John Dark at Newcastle University, UK, who wasn't involved in the work.

The new system, called OrganEx, dilutes the animal's blood in a 1-to-1 ratio with an artificial blood substitute that carries oxygen, has the correct acidity and has the right levels of electrolytes and other biochemicals. It also has 13 drugs added.

These are either existing medicines or experimental drugs, including compounds that thin the blood to stop small blood vessels getting blocked by clots, drugs that block a cell death process called necroptosis and others that have anti-inflammatory effects.

The blood substitute is also unusual in that it contains no red blood cells, which normally carry oxygen bound to a protein called haemoglobin. Instead, the fluid contains a compound called Hemopure, a form of haemoglobin obtained from cow's blood.

In 2019, Vrselja and his team reported that their system could reverse signs of cell death when connected to the brains of pigs, four hours after they had been decapitated. In the latest study, they wanted to see if the fluid could help reverse the damage that occurs in other organs after death, and to test it in whole bodies.

The pigs were put to sleep with a general anaesthetic and put on ventilators to control their breathing. Then their hearts were stopped electrically and the ventilators were turned off, at which point they would normally be considered dead.

After 1 hour, the treatments to try to restore cell function began. Six pigs were connected to the OrganEx system and six others were connected to an ordinary heart-lung machine as a comparison, with both groups' body temperature reduced to 28°C to help reduce damage. There were three further control groups, where the animals were given no treatment.

After 6 hours, the extent of blood flow was measured by injecting dye and doing scans of the animals. The pigs given the OrganEx treatment had better blood supply to their organs than the animals put on a heart-lung machine, in which many of the smaller blood vessels had collapsed.

Tests on cells and tissue samples from the animals showed that those treated with OrganEx had less cell death and had restored cell functioning, judged by measures such as how much glucose they could metabolise.

The team says the first practical use of the system may be in keeping organs for transplants healthy for longer so they can be transported further between deceased donors and people who need them.

Peter Friend at the University of Oxford says the initial results are promising, but the best way to gauge the health of the animals' organs would be to transplant them into another animal. "That lets you see if they work," he says. "If they're going after transplantation, just transplant the organ."

The system could also potentially be used to help people who have had heart attacks or strokes - when blood supply to the heart or brain, respectively, is reduced - by perfusing either of these organs with the healing fluid. "If it is successful in resuscitating an organ which has suffered an otherwise fatal injury, then potentially this is very exciting," says Friend.

Stephen Latham, an ethicist at Yale University who was part of the research team, says the more radical use of trying to "reverse death" - for instance, in treating someone some time after their heart has stopped due to drowning - would be much further in the future.

"There's a great deal more experimentation that would be required," he says. "The perfusate would have to be adapted to a human body. And you'd have to think about what is the state to which a human being would be restored. If you gave them a perfusate that reversed some but not all of that damage, that could be a terrible thing."

Journal reference: Nature, DOI: 10.1038/s41586-022-05016-1
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Blood substitute repairs damaged organs hours after heart stops

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Use of an artificial blood substitute can reverse cell damage caused by lack of oxygen and could make more organs available for transplants, treat heart attacks and strokes and even reverse death A procedure that reverses cell damage after the heart has stopped pumping blood may lead to more organ transplants and better treatments for heart attacks and strokes, and one day could even save the lives of people who would currently be considered dead.

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Eye Tests May Help Diagnose Alzheimers Disease

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Evan Hunt: Breakthrough method of Alzheimers diagnosis

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Evan Hunt: Breakthrough method of Alzheimers diagnosis

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During an embryo's development, a piece of the still-growing brain branches off to form the retina, a sliver of tissue in the back of the eye. This makes the retina, which is composed of several layers of neurons, a piece of the central nervous system. As evidence builds that changes in the brain can manifest in this region, scientists are turning to retinas as a potential screening target for early signs of Alzheimer's, an incurable neurodegenerative disease that affects an estimated six million people in the U.S. alone.

Initially clinicians could diagnose Alzheimer's only through brain autopsies after patients died. Since the early 2000s, however, research advances have made it possible to pinpoint signs of the disease-and to begin to investigate treatment-years before symptoms first appear. Today positron emission tomography (PET) brain imaging and tests of cerebrospinal fluid (CSF), the clear liquid surrounding the brain and spinal cord, aid Alzheimer's diagnosis at its early stages.

"There have been tremendous improvements in our ability to detect early disease," says Peter J. Snyder, a neuropsychologist and neuroscientist at the University of Rhode Island. But these diagnostic methods are not always readily available, and they can be expensive and invasive. PET imaging requires injecting a radioactive tracer molecule into the bloodstream, and spinal fluid must be extracted with a needle inserted between vertebrae in the back. "We need ways of funneling the right high-risk individuals into the diagnostic process with low-cost screening tools that are noninvasive and simple to administer," Snyder says. The retina is a particularly attractive target, he adds, because it is closely related to brain tissue and can be examined noninvasively through the pupil, including with methods routinely used to check for eye diseases.

One approach to retinal screening aims to search for signs of beta-amyloid, the peptide that amasses into damaging plaques in the brains of people with Alzheimer's. Studies suggest this protein fragment also accumulates in the retina-and researchers have found evidence that it may be detectable there before the onset of symptoms.

In 2014 Robert Vince and Swati More of the University of Minnesota's Center for Drug Design first described how to use a method called hyperspectral imaging, which captures an image at many different light wavelengths, to identify amyloid aggregates (clumps of beta-amyloid) in mouse retinas. They then confirmed these clumps in the animals' brains at later stages of disease. Since first reporting those findings, the two scientists and their colleagues found that amyloid aggregates may act as an early marker in human eyes, too.

The team has since licensed the technique to a Canadian medical imaging company, RetiSpec, which combines it with a machine-learning algorithm that pinpoints amyloid clumps in hyperspectral images. Investigators at multiple facilities across North America are now conducting clinical trials to examine this technique's efficacy.

Preliminary findings from the trials, presented at a conference last November, included 108 participants who either were at risk of or had preclinical Alzheimer's or mild cognitive impairment, which can be an early sign of neurodegenerative disease. After comparing the retinal screening tests with PET and CSF results, the researchers found the technique correctly identified people with brain amyloid 86 percent of the time and correctly ruled out those without it 80 percent of the time. These results are promising, says Sharon Cohen, medical director at Toronto Memory Program and leader of the trial. More data are needed before this can be rolled out as an approved diagnostic tool, Cohen adds. "But I think that day will come."

Other researchers have also reported amyloid in the retinas of people whose PET scans show amyloid plaques but who do not show signs of cognitive decline. University of California, San Diego, neuroscientist Robert Rissman and his colleagues are conducting retinal screens in participants taking part in a larger, ongoing trial of an investigative Alzheimer's drug for this population. The investigators measured retinal amyloid in a small feasibility study of eight participants, and they are now screening retinas among a larger number of patients-both before and after treatment. These data may illuminate how retinal amyloid changes over time and show whether their treatment reduces its levels, Rissman says.

Scientists are also focusing on other retinal signs of early Alzheimer's. In a study published earlier this year in JAMA Ophthalmology, researchers reported that retinal thickness was associated with certain aspects of cognitive performance. And Snyder's team has been investigating progressive changes in the retina's anatomy, such as shrinkage in certain regions; preliminary work seems to indicate a correlation with amyloid buildup in the brain. Snyder and his colleagues are now looking for these and other retina-based biomarkers, such as changes in blood vessels, as part of a longitudinal trial known as the Atlas of Retinal Imaging in Alzheimer's Study (ARIAS).

Although there are a variety of approaches to retina-based diagnosis, Rissman says that they remain unproved at this stage. He cautions that there are several open questions-including whether the protein aggregates that researchers detect are actually amyloid. Snyder points out that scientists are still debating the best method of identifying the substance in retinas and that findings from imaging studies of these protein clumps have sometimes varied from one facility to another.

Cohen, however, says that "while additional confirmatory studies in different laboratories ... are always welcome, there is sufficient evidence of amyloid deposition in the retina such that the finding should no longer be in dispute."

Early detection and accurate diagnosis are key to getting people on the right care and treatment path-and tools such as retinal imaging can aid both patients and physicians in that journey, says Rebecca Edelmayer, senior director of scientific engagement at the Alzheimer's Association. Even though the full potential of retinal imaging has yet to be determined, she adds, "it's a really interesting time in this space."

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Eye Tests May Help Diagnose Alzheimer’s Disease

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During an embryo's development, a piece of the still-growing brain branches off to form the retina, a sliver of tissue in the back of the eye. This makes the retina, which is composed of several layers of neurons, a piece of the central nervous system.

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Risk of Volcano Catastrophe ' a roll of the dice' (Josh Sharo)

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Risk of Volcano Catastrophe ' a roll of the dice' (Josh Sharo)

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This article talks about the problems that volcanos can cause with the bigger number of people on earth. My question is what would happen if there was a close to Pompeii level event with the amount of people there are on earth.

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The world is "woefully underprepared" for a massive volcanic eruption and the likely repercussions on global supply chains, climate and food, according to experts from the University of Cambridge's Centre for the Study of Existential Risk (CSER), and the University of Birmingham.

In an article published in the journal Nature, they say there is a "broad misconception" that risks of major eruptions are low, and describe current lack of governmental investment in monitoring and responding to potential volcano disasters as "reckless."

However, the researchers argue that steps can be taken to protect against volcanic devastation -- from improved surveillance to increased public education and magma manipulation -- and the resources needed to do so are long overdue.

"Data gathered from ice cores on the frequency of eruptions over deep time suggests there is a one-in-six chance of a magnitude seven explosion in the next one hundred years. That's a roll of the dice," said article co-author and CSER researcher Dr Lara Mani, an expert in global risk.

"Such gigantic eruptions have caused abrupt climate change and collapse of civilisations in the distant past."

Mani compares the risk of a giant eruption to that of a 1km-wide asteroid crashing into Earth. Such events would have similar climatic consequences, but the likelihood of a volcanic catastrophe is hundreds of times higher than the combined chances of an asteroid or comet collision.

"Hundreds of millions of dollars are pumped into asteroid threats every year, yet there is a severe lack of global financing and coordination for volcano preparedness," Mani said. "This urgently needs to change. We are completely underestimating the risk to our societies that volcanoes pose."

An eruption in Tonga in January was the largest ever instrumentally recorded. The researchers argue that if it had gone on longer, released more ash and gas, or occurred in an area full of critical infrastructure -- such as the Mediterranean -- then global shock waves could have been devastating.

"The Tonga eruption was the volcanic equivalent of an asteroid just missing the Earth, and needs to be treated as a wake-up call," said Mani.

The CSER experts cite recent research detecting the regularity of major eruptions by analysing traces of sulphur spikes in ancient ice samples. An eruption ten to a hundred times larger than the Tonga blast occurs once every 625 years -- twice as often as had been previously thought.

"The last magnitude seven eruption was in 1815 in Indonesia," said co-author Dr Mike Cassidy, a volcano expert and visiting CSER researcher, now based at the University of Birmingham.

"An estimated 100,000 people died locally, and global temperatures dropped by a degree on average, causing mass crop failures that led to famine, violent uprisings and epidemics in what was known as the year without summer," he said.

"We now live in a world with eight times the population and over forty times the level of trade. Our complex global networks could make us even more vulnerable to the shocks of a major eruption."

Financial losses from a large magnitude eruption would be in the multi-trillions, and on a comparable scale to the pandemic, say the experts.

Mani and Cassidy outline steps they say need to be taken to help forecast and manage the possibility of a planet-altering eruption, and help mitigate damage from smaller, more frequent eruptions.

These include a more accurate pinpointing of risks. We only know locations of a handful of the 97 eruptions classed as large magnitude on the "Volcano Explosivity Index" over the last 60,000 years. This means there could be dozens of dangerous volcanoes dotted the world over with the potential for extreme destruction, about which humanity has no clue.

"We may not know about even relatively recent eruptions due to a lack of research into marine and lake cores, particularly in neglected regions such as Southeast Asia," said Cassidy. "Volcanoes can lie dormant for a long time, but still be capable of sudden and extraordinary destruction."

Monitoring must be improved, say the CSER experts. Only 27% of eruptions since 1950 have had a seismometer anywhere near them, and only a third of that data again has been fed into the global database for "volcanic unrest."

"Volcanologists have been calling for a dedicated volcano-monitoring satellite for over twenty years," said Mani. "Sometimes we have to rely on the generosity of private satellite companies for rapid imagery."

The experts also call for increased research into volcano "geoengineering." This includes the need to study means of countering aerosols released by a massive eruption, which could lead to a "volcanic winter." They also say that work to investigate manipulating pockets of magma beneath active volcanoes should be undertaken.

Added Mani: "Directly affecting volcanic behaviour may seem inconceivable, but so did the deflection of asteroids until the formation of the NASA Planetary Defense Coordination Office in 2016. The risks of a massive eruption that devastates global society is significant. The current underinvestment in responding to this risk is simply reckless."

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volcanoes; natural disasters; climate; early climate; fossils; origin of life; environmental policies; resource shortage; disaster plan

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Risk of volcano catastrophe 'a roll of the dice'

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The world is "woefully underprepared" for a massive volcanic eruption and the likely repercussions on global supply chains, climate and food, according to experts from the University of Cambridge's Centre for the Study of Existential Risk (CSER), and the University of Birmingham.

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This article outlines how a group of students enrolled in the University of Illinois, successfully modified the photoreceptors within soybean plants in order to increase efficiency and yields of photosynthesis.

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Bioengineering: Better photosynthesis increases yields in food crops

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Scientists have transgenically altered soybean plants to increase the efficiency of photosynthesis, resulting in greater yields without loss of quality.

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Declan Halos: Turning Greenhouse Gases for the Good

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Declan Halos: Turning Greenhouse Gases for the Good

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One professor from TU Wien, has found a sustainable method to turn the most devastating greenhouse gases such as Carbon Dioxide and Methane into sustainable gases which produce energy. This process in short is taking harmful gases to create non-harmful gases both in the name of energy creation.

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Turning CO2 and methane into valuable products, effectively

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CO2 and methane can be turned into valuable products. But there is a problem with the catalysts required for this: They end up being covered in a layer of carbon, losing their effectivity. A new catalyst has now been developed which solves this problem and can be used for a long time.

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A clever molecular trick extends the lives of these ant queens (Josh Sharo)

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A clever molecular trick extends the lives of these ant queens (Josh Sharo)

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This article talks about the abnormally long life that queen ants live. It is said that they have a certain self-produced insulin blocker. My question is how do the other ants not have this same insulin blocker?

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For some ant queens, the secret to long life might be a self-produced insulin blocker.

Ant queens are famously long-lived, even though they shouldn't be. Generally, animals that put lots of energy into reproduction sacrifice some time off their life. But ant queens produce millions of eggs and live an extraordinarily long time compared with worker ants that don't reproduce.

Now, researchers have shown how one ant species pulls off this anti-aging feat. When queens and wannabe queens of the species Harpegnathos saltator gear up to reproduce, a part of what's called the insulin signaling pathway gets blocked, slowing aging, the researchers report in the Sept. 2 Science. That molecular pathway has long been implicated in aging in mammals, including humans.

"There's been a need to understand why queens, or reproductives, in social insects can live for so amazingly long," says Marc Tatar, a biologist at Brown University in Providence, R.I., who was not involved with the study. Some ant species have queens that survive 30 times as long as their workers. Other social insects such as bees and termites also have long-lived queens.

In a rare behavior for ants, when a queen H. saltator dies, some female workers begin competing in duels for the chance to replace her ( SN: 1/17/14). These hopeful royals develop ovaries, start laying eggs and transition into queenlike forms called gamergates. When a worker transitions to a gamergate, her life span becomes five times as long as it was. But if she doesn't end up becoming queen and reverts back to a worker, her life span shortens again.

The researchers exploited this behavior to investigate the molecular underpinnings of anti-aging in these ants. H. saltator gamergates, it turns out, extend their life spans by taking advantage of a split in the insulin signaling pathway, the chain of chemical reactions that drive insulin's effects on the body. One branch of this pathway is involved with reproduction, while the other is implicated in aging.

"Insulin comes with our life - [after] we eat, we have high insulin," says Hua Yan, a biologist at the University of Florida in Gainesville. "But a constant high level of insulin is bad for longevity."

Examining patterns of gene activity, Yan and colleagues found that gamergates have more active insulin genes than regular worker ants and, as a result, have increased metabolic activity and ovary development. But the secret sauce protecting the ants from the insulin's aging effects appears to be a molecule called Imp-L2, which blocks the branch of the insulin pathway linked to aging, experiments showed. The branch involved in reproduction, however, remains active.

"What we don't understand is how Imp-L2 can act on one aspect of the pathway and not on the other," says study coauthor Claude Desplan, a developmental biologist at New York University.

These results represent a leap forward in our understanding of extreme social insect longevity, the researchers say, while also showcasing an anti-aging evolutionary adaptation that hasn't been seen in the wild before.

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A clever molecular trick extends the lives of these ant queens

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For some ant queens, the secret to long life might be a self-produced insulin blocker. Ant queens are famously long-lived, even though they shouldn't be. Generally, animals that put lots of energy into reproduction sacrifice some time off their life. But ant queens produce millions of eggs and live an extraordinarily long time compared with worker ants that don't reproduce.

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Reynolds Barringer : Who has the highest risk of long COVID?

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Reynolds Barringer : Who has the highest risk of long COVID?

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This article talks about millions of people who after they tested negative for COVID had symptoms long after. The article explains what life with long COVID is like.

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This article piqued my interest because this ancient critter was once believed to be the oldest animal in the widest ranging species group, containing everything from starfish to humans.

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No ifs, ands or butts about it: A teeny roughly 530-million-year-old critter that lacks an anus is not, as previously thought, the oldest member of a wide-ranging animal group that includes everything from starfish to humans.

Despite its absent anus, Saccorhytus coronarius had no shortage of holes on its wrinkly potato-shaped body, including a ring of small openings around its gaping mouth. Previously, those holes had been identified as an early version of gill slits, typically used for respiration ( SN: 2/3/17). Gill slits are commonly found in deuterostomes, so their presence seemingly nailed the critter's spot on the animal family tree.

But a new 3-D reconstruction of the half-millimeter-long species based on fossil imaging shows those holes are instead remnants of broken spines, researchers report August 17 in Nature. The identification of the spines helped shift the creature into a group with arthropods and nematodes, called Ecdysozoa.

After millions of years, fossils can look very different from the original specimens, which makes it challenging to identify biological features ( SN: 3/8/22). Most S. coronarius fossils have been flattened "like a very sad balloon that's collapsed in on itself," says paleontologist Philip Donoghue of the University of Bristol in England. The 3-D reconstruction brings S. coronarius to life - even if it does look something like an angry minion, he says.

Donoghue and his colleagues took X-rays of many S. coronarius fossils representing different stages of the organisms' decay. The images revealed that an inner skin layer once pushed through pores and extended outward, forming spines. During fossilization, that inner layer was lost, and the holes were left behind.

While the spines pretty much lock S. coronarius into its new group, a puzzle remains: the absent anus. It's not inherently weird - the absence has evolved independently in many species such as jellyfish, which vomit their food waste. But both deuterostomes and ecdysozoans usually have anuses, making S. coronarius an uncomfortable fit in either group.

Still, "if you haven't got an anus," Donoghue jokes, "you're not going to be very comfortable anywhere."

Questions or comments on this article? E-mail us at feedback@sciencenews.org

Anna Gibbs was the spring 2022 science writing intern at Science News. She holds a B.A. in English from Harvard College.

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This bizarre ancient critter has been kicked out of a group that includes humans

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No ifs, ands or butts about it: A teeny roughly 530-million-year-old critter that lacks an anus is not, as previously thought, the oldest member of a wide-ranging animal group that includes everything from starfish to humans. Despite its absent anus, Saccorhytus coronarius had no shortage of holes on its wrinkly potato-shaped body, including a ring of small openings around its gaping mouth.

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Ben Statis: The One-Two Punch on The Dinosaurs

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Ben Statis: The One-Two Punch on The Dinosaurs

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Contrary to one of the most popular beliefs, scientists have discovered the remains of a crater off the coast of West Africa, which was believed to have formed around the same time as the crater that wiped out the dinosaurs. If confirmed, it could mean that nonbird dinosaurs met their demise by a one-two punch of asteroids, researchers report in the Aug. 17 Science Advances.

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Chicxulub, the asteroid that wiped out most dinosaurs, might have had a little sibling.

Off the coast of West Africa, hundreds of meters beneath the seafloor, scientists have identified what appears to be the remains of an 8.5-kilometer-wide impact crater, which they've named Nadir. The team estimates that the crater formed roughly around the same time that another asteroid - Chicxulub, the dinosaur killer - slammed into modern day Mexico ( SN: 1/25/17). If confirmed, it could mean that nonbird dinosaurs met their demise by a one-two punch of asteroids, researchers report in the Aug. 17 Science Advances.

"The idea that [Chicxulub] had help - for want of a better phrase - would have really added insult to serious injury," says study coauthor Veronica Bray, a planetary scientist at the University of Arizona in Tucson.

Nearly 200 impact craters have been discovered on Earth ( SN: 12/18/18), the vast majority of which are on land. That's because impact craters at sea gradually become buried under sediment, Bray says, which makes the Nadir structure a valuable scientific find, regardless of its birthdate.

Geologist Uisdean Nicholson of Heriot-Watt University in Edinburgh happened upon the structure while analyzing data collected by seismic waves transmitted underground to detect physical structures offshore of Guinea. Lurking beneath the seafloor - and under nearly 1 kilometer of water - he discerned a bowl-shaped structure with a broken-up, terraced floor and a pronounced central peak - features expected of a large impact.

Based on the structure's dimensions, Bray, Nicholson and their colleagues calculate that, if an asteroid was responsible for the terrain, it would probably have been over 400 meters wide. What's more, the researchers estimate that the impact would have rocked the ground like a magnitude 7 earthquake and stirred tsunamis hundreds of meters high.

Despite that fallout, the Nadir impact would have been far less devastating than the one from the roughly 10-kilometer-wide Chicxulub asteroid, says Michael Rampino, a geologist from New York University who was not involved in the study. "It certainly wouldn't have had global effects," he says.

Using geologic layers adjacent to Nadir, some with ages obtained by past studies, the team estimated the structure to have formed around the end of the Cretaceous period - 66 million years ago. The Nadir asteroid may even have formed a pair with the Chicxulub asteroid, the two having been ripped apart by gravitational forces during a previous Earth flyby, the researchers speculate.

But the study's conclusions have some experts wary. "It looks like an impact crater, but it could also be something else," says geologist Philippe Claeys of Vrije Universiteit Brussel in Belgium, who was not involved in the research. Confirming that the structure is an impact crater will require drilling for solid evidence, such as shocked quartz, he says. Alternative explanations for the structure's identity include a collapsed volcanic caldera or a squeezed body of salt called a salt diapir.

The Nadir structure's age is another uncertainty. The seismic data shows it appears to have formed sometime near the end the Cretaceous period or maybe a little later, Claeys says. "But that's around the best they can say." Drilling in the crater for minerals that contain radioactive elements could provide a more precise date of formation, Rampino says.

It's not the first time that scientists have investigated whether Chicxulub had an accomplice. Some studies have suggested that the Boltysh crater in Ukraine may have formed at the same time as Chicxulub, though researchers have since determined that Boltysh formed 650,000 years later.

Bray and her colleagues are currently negotiating for funding to collect samples from the crater, with aspirations to drill in 2024. That will hopefully settle some of the debate surrounding Nadir's origins, Bray says, though new questions will probably arise too. "If we do prove that this is the sister of the dinosaur killer, then how many other siblings are there?"

Questions or comments on this article? E-mail us at feedback@sciencenews.org

Nikk Ogasa is a staff writer who focuses on the physical sciences for Science News. He has a master's degree in geology from McGill University, and a master's degree in science communication from the University of California, Santa Cruz.

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Not one, but two asteroids might have slain the dinosaurs

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Chicxulub, the asteroid that wiped out most dinosaurs, might have had a little sibling. Off the coast of West Africa, hundreds of meters beneath the seafloor, scientists have identified what appears to be the remains of an 8.5-kilometer-wide impact crater, which they've named Nadir.

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Reynolds Barringer : Drugs that mutate viruses to kill them could make them more dangerous

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Reynolds Barringer : Drugs that mutate viruses to kill them could make them more dangerous

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This article speaks on drugs that can initially be helpful, but in the long run be hurtful to people.

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Tristan Roux: Spiky ‘Sleep Spindles’ Linked to Acts of Learning

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Tristan Roux: Spiky ‘Sleep Spindles’ Linked to Acts of Learning

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This article discusses how certain spikes in brain activity (spindles) can cause increase recollection of information. It is said that those who study and then take a nap tend to have strong spindles in the early sleep stages. If we can pinpoint what causes this is there a way we can self induce it one day?

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Advertisement

Distinctive bursts of sleeping-brain activity, known as sleep spindles, have long been generally associated with strengthening recently formed memories. But new research has managed to link such surges to specific acts of learning while awake.

These electrical flurries, which can be observed as sharp spikes on an electroencephalogram (EEG), tend to happen in early sleep stages when brain activity is otherwise low. A study published in Current Biology shows that sleep spindles appear prominently in particular brain areas that had been active in study participants earlier, while they were awake and learning an assigned task. Stronger spindles in these areas correlated with better recall after sleep.

"We were able to link, within [each] participant, exactly the brain areas used for learning to spindle activity during sleep," says University of Oxford cognitive neuroscientist Bernhard Staresina, senior author on the study. Staresina, Marit Petzka of the University of Birmingham in England and their colleagues devised a set of tasks they called the "memory arena," which required each participant to memorize a sequence of images appearing inside a circle. While the subjects did so, researchers measured their brain activity with an EEG, which uses electrodes placed on the head. Participants then took a two-hour nap, after which they memorized a new image set-but then had to re-create the original image sequence learned before sleeping.

During naps, the researchers recorded stronger sleep spindles in the specific brain areas that had been active during the pre-sleep-memorization task, and these areas differed for each participant. This suggested that the spindle pattern was not "hardwired" in default parts of the human brain; rather it was tied to an individual's thought patterns. The researchers also observed that participants who experienced stronger sleep spindles in brain areas used during memorization did a better job re-creating the images' positions after the nap.

Previous research suggested spindles trigger brain changes that start the process of strengthening and refining a memory, in part by controlling the influx of calcium to certain cells. The new study is the first to directly measure brain activity during learning to support such a link and the first to associate better memory recall with stronger spindles in areas that had been active during learning, the researchers say-although they note it does not indicate whether spindles themselves actively improved recall. Staresina says that future work should examine spindle and other activity in the hippocampus, the brain's memory hub.

The study is "a convincing manuscript that supports the role of spindles in memory," says Lourdes DelRosso, a sleep researcher and physician at the University of Washington and Seattle Children's Hospital, who was not involved in the work. She hopes scientists also investigate spindles in people with conditions that affect learning and attention, such as ADHD and dyslexia.

This article was originally published with the title "Memory Spikes" in Scientific American 327, 3, 20 (September 2022)

doi:10.1038/scientificamerican0922-20a

ABOUT THE AUTHOR(S)

Rebecca Sohn is a freelance health and science journalist based in New York City. She has written for outlets such as Slate, Spectrum, STAT and Live Science, among others.

Recent Articles by Rebecca Sohn

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Spiky ‘Sleep Spindles’ Linked to Acts of Learning

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Distinctive bursts of sleeping-brain activity, known as sleep spindles, have long been generally associated with strengthening recently formed memories. But new research has managed to link such surges to specific acts of learning while awake. These electrical flurries, which can be observed as sharp spikes on an electroencephalogram (EEG), tend to happen in early sleep stages when brain activity is otherwise low.

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Tristan Roux: Scientists turned dead spiders into robots

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Tristan Roux: Scientists turned dead spiders into robots

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In the article we learn that spiders legs curl up when they die due to a loss of blood pressure. Scientist wanted to see if they could mimic the spider pushing blood into its legs to extend them by pushing fluid into them. This proved to turn the spiders into a claw like machine that was good for picking wires and could withstand wear over 100 uses. Is this a new step to building more advanced robots/bionics or is playing with the dead going to blow up in our faces?

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Scientists have literally reanimated dead spiders to do their bidding.

In a new field dubbed "necrobotics," researchers converted the corpses of wolf spiders into grippers that can manipulate objects. All the team had to do was stab a syringe into a dead spider's back and superglue it in place. Pushing fluid in and out of the cadaver made its legs clench open and shut, the researchers report July 25 in Advanced Science.

The idea was born from a simple question, explains Faye Yap, a mechanical engineer at Rice University in Houston. Why do spiders curl up when they die?

The answer: Spiders are hydraulic machines ( SN: 4/25/22). They control how much their legs extend by forcing blood into them. A dead spider no longer has that blood pressure, so its legs curl up.

"We were just thinking that was so cool," Yap says. "We wanted to leverage it."

Her team first tried putting dead wolf spiders in a double boiler, hoping that the wet heat would make the spiders expand and push their legs outward. That didn't work. But when the researchers injected fluid straight into a spider corpse, they found that they could control its grip well enough to pull wires from a circuit board and pick up other dead spiders. Only after hundreds of uses did the necrobots start to become dehydrated and show signs of wear.

T.F. Yap and coauthors

In the future, the researchers will coat spiders with a sealant to hold off that decline. But the next big step is to control the spiders' legs individually, Yap says, and in the process, figure out more about how spiders work. Then her team could translate their understanding into better designs for other robots.

"That would be very, very interesting," says Rashid Bashir, a bioengineer at the University of Illinois Urbana-Champaign who wasn't involved in the new study. A spider corpse itself would probably have problems as a robot, he says, because it won't perform consistently like "hard robots" and its body will break down over time. But spiders can definitely offer lessons to engineers ( SN: 4/2/19). "There's a lot to be learned from biology and nature," Bashir says.

Despite the whole reanimating dead spiders thing, Yap is no mad scientist. She wonders whether it's okay to play Frankenstein, even with spiders. "No one really talks about the ethics" when it comes to this sort of research, she says.

Scientists need to figure out the morality of this sort of bioengineering before they get too good at it, Bashir agrees. The question is, he says, "how far do you go?"

Questions or comments on this article? E-mail us at feedback@sciencenews.org

Asa Stahl is the 2022 AAAS Mass Media fellow with Science News. He is a 5th year Astrophysics Ph.D. student at Rice University, where his research focuses on detecting and characterizing young stars and planets.

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Scientists turned dead spiders into robots

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In a new field dubbed “necrobotics,” researchers used a syringe and some superglue to control the dead bodies of wolf spiders.

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Jennifer Park: Vegetarian women are at a higher risk of hip fracture

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Jennifer Park: Vegetarian women are at a higher risk of hip fracture

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The article talks about how more than 26,000 middle-aged women following a vegetarian diet are at a 33% more risk of a hip fracture. It describes how plant-based diets are becoming popular, which raises the question if vegetarian diets can be healthy or unhealthy.

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A large study tracking women in the UK finds that vegetarians have a higher risk of breaking a hip compared with women who eat any amount of meat

The risk of breaking a hip is a third higher for women who are vegetarian than those who are regular meat eaters, according to a large UK study.

The increase in risk may arise from meat-free diets tending to have less protein, which helps build muscle mass, and possible deficiencies in vitamins and minerals, such as calcium and vitamin B12, which help strengthen bones.

Women are more likely to break their hips than men, especially as they get older, because after the menopause, levels of the sex hormone oestrogen fall, leading to weaker bones. Broken hips are a significant cause of deaths in older people as they are hard to recover from and can result in extended immobility and health complications. "The effect on health is pretty big," says James Webster at the University of Leeds, UK.

Previous studies have suggested that vegetarians and vegans have weaker bones, so Webster's team took advantage of a large ongoing study that has tracked the health and lifestyle of over 26,000 women in the UK for about 20 years. They were aged between 35 and 69 at recruitment, and none were transgender as far as the researchers know.

Overall, about 3 per cent of participants broke their hip during that time. Those who were vegetarian had a 33 per cent higher risk of this happening compared with those who consumed meat at least five times a week.

There was no difference in risk between regular meat eaters and those who ate lesser amounts, or just ate fish. Vegans weren't included in the study.

Other research has found that being vegetarian is better for health in different ways - for instance, it is linked with a lower risk of heart disease. All such studies, including the latest one, are observational, however, and so can't prove that diet causes different health patterns - only that there are correlations.

Such studies can make meat-free diets seem more beneficial than they really are because vegetarians usually have healthier lifestyles in other ways, such as avoiding smoking and heavy drinking. The best kind of medical evidence comes from randomised trials, but these are hard to do for a major dietary choice such as whether or not to eat meat.

Webster says the latest findings shouldn't make people quit vegetarianism, as people can get protein from dairy products and pulses and can take vitamin supplements or use calcium-fortified dairy products if necessary.

Jen Elford at the Vegetarian Society says: "It is important to keep this issue in proportion - outcomes for the health of vegetarians are generally very good. Fracture risk is generally correlated with intake of calcium and vitamin D and so the need to ensure reliable intakes of these nutrients is highlighted."

Journal reference: BMC Medicine, DOI: 10.1186/s12916-022-02468-0
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Vegetarian women have 33 per cent higher risk of breaking a hip

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A large study tracking women in the UK finds that vegetarians have a higher risk of breaking a hip compared with women who eat any amount of meat The risk of breaking a hip is a third higher for women who are vegetarian than those who are regular meat eaters, according to a large UK study.

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Will Rudisill: Pesticides and their harmful effects 

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Will Rudisill: Pesticides and their harmful effects 

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This article demonstrates how pesticides are harming our environment.

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Pesticides Are Killing the Organisms That Keep Our Soils Healthy

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They harm worms, beetles and thousands of other subterranean species that are vital to agriculture

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Jennifer Park: Most plant milks are lower in key micronutrients than cow's milk

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Jennifer Park: Most plant milks are lower in key micronutrients than cow's milk

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The article discusses how plant-based milk has lower micronutrients than cow's milk. There are many reasons why people choose plant milk over cow's milk, whether for ethical issues or diet, but if their primary reason is for the nutrients, then plant-based milk would not be the choice.

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Cow's milk is an important source of phosphorus, magnesium, zinc and selenium, but tests show these nutrients are lacking in most plant milks except pea milk

Most plant-based "milks" have lower amounts of four key micronutrients - phosphorus, magnesium, zinc and selenium - than cow's milk. The exception is milk substitutes made from pea protein, which has broadly similar levels to cow's milk.

The findings come from the first large study to compare levels of these four minerals in eight different plant-based milk substitutes, carried out by the US Food and Drug Administration (FDA).

Alternative milks - which are generally made by grinding up produce such as almonds, oats or rice, soaking it in water and adding emulsifiers and stabilisers - have been growing in popularity in recent years, both among vegans, who eat no animal products, and others who avoid dairy for ethical or environmental reasons.

Plant milks are often naturally lower in calcium and iodine, but may be fortified with these nutrients, and producers in the US are required to state their concentration on packaging. But levels of some other minerals, including magnesium, phosphorus, zinc and selenium, aren't required to be on the label and yet milk and other dairy products are usually a major source of them in the US diet, says Benjamin Redan of the FDA.

Redan's team analysed levels of the four minerals in 85 samples of plant milks, made from almond, cashew, coconut, hemp, oat, pea, rice and soya. They found that while pea milk was similar to cow's milk in terms of these nutrients, other products had lower levels of most of the minerals.

Almond milk, for instance, has about one-ninth the phosphorus concentration of cow's milk. Phosphorus is needed for growth and tissue repair, as well as helping the body use substances such as vitamin D and iodine. Oat milk has about the same levels as cow's milk.

All the products apart from pea milk had much lower levels of selenium than cow's milk. Selenium is needed for a healthy immune system.

"Those who consume plant-based milk alternatives lower in these target minerals should seek to obtain these nutrients through other foods or beverages," says Redan.

"All of those nutrients can be obtained from other sources, such as nuts, seeds and lentils," says Clare Thornton-Wood, a spokesperson for the British Dietetic Association.

Chantal Tomlinson at the UK's Vegan Society says people eating a plant-based diet would get enough of the minerals in question if they eat a balanced diet containing a variety of whole-plant foods, fortified foods and supplements. "It is not necessary for plant alternatives to cow's milk to supply equivalent amounts of all nutrients," she says.

The findings were presented today at the American Chemical Society Fall meeting in Chicago.

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Most plant milks are lower in key micronutrients than cow's milk

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Cow's milk is an important source of phosphorus, magnesium, zinc and selenium, but tests show these nutrients are lacking in most plant milks except pea milk Most plant-based "milks" have lower amounts of four key micronutrients - phosphorus, magnesium, zinc and selenium - than cow's milk.

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This article demonstrates how scientists have searched for ways to regulate the use of pesticides.

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Adjusting pesticide regulation and use in European soils: The risks that pesticides can pose for non-target organisms according to soil type in three European areas are analysed

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Scientists have explored how to improve the PERSAM model used by the European Food Safety Authority (EFSA) in pesticide regulation. They have analysed the risks posed by four pesticides on two types of soil organisms in northern, central and southern Europe.

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McKenna Stout: The Extinction of "Demon Ducks" as Linked to Slow Development

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McKenna Stout: The Extinction of "Demon Ducks" as Linked to Slow Development

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https://www.mdpi.com/1424-2818/13/3/124

The article, as well as scientific research article (link listed above) ^ talks about an extinct species of bird that stood 3 meters tall, and grew to unimaginable weights. Through analyzing the bone structures of their legs, scientists have discovered that these bird grew at an extremely slow rate, taking up to 15 years to mature. That slow growth rate was likely associated with their demise.

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Giant flightless birds called mihirungs were the biggest birds to ever stride across what is now Australia. The animals, which weighed up to hundreds of kilograms, died out about 40,000 years ago. Now researchers might have a better idea why.

The birds may have grown and reproduced too slowly to withstand pressures from humans' arrival on the continent, researchers report August 17 in the Anatomical Record.

Mihirungs are sometimes called "demon ducks" because of their great size and close evolutionary relationship with present-day waterfowl and game birds. The flightless, plant-eating birds lived for more than 20 million years.

Over that time, some species evolved into titans. Take Stirton's thunderbird ( Dromornis stirtoni). It lived about 7 million years ago, stood 3 meters tall and could exceed 500 kilograms in weight, making it the largest-known mihirung and a contender for the largest bird ever to live.

Most research on mihirungs has been on their anatomy and evolutionary relationships with living birds. Little is known about the animals' biology, such as how long they took to grow and mature, says Anusuya Chinsamy-Turan, a paleobiologist at the University of Cape Town in South Africa.

So Chinsamy-Turan and colleagues at Flinders University in Adelaide, Australia took samples from 20 fossilized leg bones of D. stirtoni, from animals of varying life stages.

Flinders Univ.

"Even after millions of years of fossilization, the microscopic structure of fossil bones generally remains intact," and it can be used to decipher important clues about extinct animals' biology, Chinsamy-Turan says.

The team examined the thin bone slices under a microscope, detailing the presence or absence of growth marks. These marks provide information on how fast the bone grew while the birds were alive.

D. stirtoni took 15 years or more to reach full size, the team found. It probably became sexually mature a few years before that, based on the timing of a shift from rapidly growing bone to a slower-growing form that's thought to be associated with reaching reproductive age.

These results differ from the team's earlier analysis of the bones of another mihirung, Genyornis newtoni. That species - the last-known mihirung - was less than half the size of D. stirtoni. It lived as recently as about 40,000 years ago and was a contemporary of the continent's earliest human inhabitants. G. newtoni grew up much faster than its giant relative, reaching adult size in one to two years and growing a bit more in the following years and possibly reproducing then.

This difference in how fast mihirung species that were separated by millions of years developed may have been an evolved response to Australia developing a drier, more variable climate over the last few million years, the researchers say. When resources are unpredictable, growing and reproducing quickly can be advantageous.

Even so, that seeming pep in the developmental step of more recent mihirungs was still slower than that of the emus they lived alongside. Emus grow up quickly, reaching adult size in less than a year and reproducing not long after, laying large numbers of eggs.

This difference may explain why G. newtoni went extinct shortly after hungry humans arrived in Australia, yet emus continue to thrive today, the team says. Even though over millions of years, mihirungs as a group seem to have adapted to growing and reproducing quicker than they used to, it wasn't enough to survive the arrival of humans, who probably ate the birds and their eggs, the researchers conclude.

"Slowly growing animals face dire consequences in terms of their reduced ability to recover from threats in their environments," Chinsamy-Turan says.

The scientists' research on other giant, extinct, flightless birds thought to have met their end thanks to humans - such as the dodos of Mauritius ( Raphus cucullatus) and the largest of Madagascar's elephant birds ( Vorombe titan) - shows that they too grew relatively slowly ( SN: 8/29/17).

"It is very interesting to see this pattern repeating again and again with many large, flightless bird groups," says Thomas Cullen, a paleoecologist at Carleton University in Ottawa who was not involved with the new study.

Modern ratite birds seem to be the exception in their ability to handle similar pressures, he says. Other ratites besides emus that have survived until the present day - such as cassowaries and ostriches - also grow and reproduce quickly ( SN: 4/25/14).

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Ancient 'demon ducks' may have been undone by their slow growth

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Giant flightless birds called mihirungs were the biggest birds to ever stride across what is now Australia. The animals, which weighed up to hundreds of kilograms, died out about 40,000 years ago. Now researchers might have a better idea why.

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McKenna Stout: DNA Evidence Supporting Domestication History in Dogs

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McKenna Stout: DNA Evidence Supporting Domestication History in Dogs

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https://www.nature.com/articles/s41586-022-04824-9

The scientific journal that I found above ^ talks about new DNA evidence found in a wolf skull that connects modern day dogs to two separate wolf breeds. Scientists are now analyzing DNA structures in the fossils of ancient and current dog breeds to provide new insights into just how the human species domesticated the most popular pet in the world.

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O ne lab full of rats looks pretty much the same as another. But visiting a lab in Siberia, geneticist Alex Cagan can distinguish rats bred to be tame from those bred to be aggressive as soon as he opens the lab door.

"It's a completely different response immediately," he says. All of the tame rats "come to the front of the cage very inquisitively." The aggressive rats scurry to the backs of their cages to hide. Exactly how 70 generations of breeding have ingrained friendly or hostile behaviors in the rats' DNA is a mystery that domestication researchers are trying to solve. The rats, along with mink and silver foxes, are part of a long-running study at the Institute of Cytology and Genetics in Novosibirsk, Russia. The aim is to replay domestication to determine the genetic underpinnings that set domesticated animals apart from their wild ancestors.

Surprising stories in domestication

Over thousands of years, humans have found ways to put other species to work, from spinning silk to storing water. These short stories reveal how humans got to know some of their closest companions.

Anecdotes from the annals of domestication appear along the right with illustrations.

Jody Hewgill

For thousands of years, humans have lived with animals. Some of the creatures are companions - hopping onto laps, ready to play fetch. Some have jobs - carrying heavy loads, pulling wagons and plows, and herding other animals. Others provide meat, eggs or milk. Plants, too, have been tamed. On nearly every continent, fruits, vegetables, grains, nuts and tubers stand in soldier-straight rows and yield bounty on schedule.

There was a time when the species that now inhabit humans' homes, fields and barnyards didn't exist. Then some people, somewhere, brought wild things under human control. Or the wild creatures exploited new ecological niches created by humans, gradually habituating themselves to people and, in essence, domesticating themselves. Both paths - scientists are still debating which was more likely for different animals - led to the creation of domesticated species or subspecies genetically distinct from their wild ancestors.

Scientists studying evolution and human history want to know how ancient people domesticated animals and plants. What species did humans start with and where did it happen first? How long did it take? Does one group get credit for taming wild horses or subjugating aurochs into milk-giving cows? Or did multiple people in different places have the same idea?

Even for dogs, humans' oldest, closest friends, "all those things are unknown," says evolutionary geneticist Greger Larson of the University of Oxford. For many domesticated creatures, the questions outweigh the answers. As new studies flood in - some based on archaeology, others on modern or ancient DNA - the waters get muddy, with one study's results contradicting another's.

"Domestication research right now is really going through an exciting phase," Larson says. Comparing the genetic instruction books, or genomes, of wild and domesticated species is giving evolutionary geneticists fresh clues about the changes that separate domesticated species from wild ones. New techniques (some developed in the last two to three years) for analyzing fragile DNA from ancient bones offer genetic snapshots of domestication as it played out long ago. Marrying that DNA data with archaeological findings, the context in which the bones were discovered, for example, may tell researchers more about when, where and how humans first engaged with plants and animals. Recent results are already rewriting the stories of rice, horse and chicken domestication.

A new hypothesis is also shining a light on core changes in the embryos of many domesticated species. The hypothesis aims to explain how the process of becoming close to people produces comparable changes in the appearance, reproduction and physiology of a whole range of domesticated animals. One central developmental change - in a temporary clump of cells called the neural crest - may be behind the suite of characteristics known as domestication syndrome.

The pace of research, much of it seemingly contradictory, will only increase in the near future, Larson predicts. "We're going to get a lot more confused before we figure out what's really going on."

FROM TOP: L. ORLANDO/NATURAL HISTORY MUSEUM OF DENMARK, CNRS; P. JENSEN; DARIA SHEPELEVA

Defining domestication

Deciding when an animal can be called "domesticated" isn't always easy.

Since 2002, Anna Kukekova has been making annual treks to Novosibirsk. A geneticist at the University of Illinois at Urbana-Champaign, she travels to Siberia each year to collect blood from hundreds of silver foxes to look for genetic changes that produce tame and aggressive behaviors.

These foxes are special. They are part of a long-running biological experiment to repeat domestication by turning a wild canid - from the family of animals including wolves, foxes, jackals and dogs - into a fox version of a domestic dog (SN: 5/13/17, p. 29). The project was the brainchild of geneticist Dmitry Belyaev. In the 1950s, Belyaev and colleagues started selecting and breeding the least aggressive and fearful silver foxes from those on a fur farm. Since 1960, researcher Lyudmila Trut and her team have selected the farm's friendliest foxes to breed. Over more than 60 generations, the foxes have grown more and more tolerant of humans. Kukekova says she's noticed a difference even in the 15 years she's been visiting the farm.

Keeping silkworms secret

In China, people began domesticating the larvae of silk moths for the fine, strong threads of their cocoons as early as 7,500 years ago, genetic evidence suggests. People bred the larvae to produce more silk and to tolerate human handling and extreme crowding (SN Online: 8/27/09). For more than 2,000 years, the Chinese kept their silk-making methods top secret, and smuggling silkworms out of the country was punishable by death. Silk makers traded their monopolized fabric throughout Eurasia along the Silk Road (SN: 5/27/17, p. 4). To this day, the only other insect that is domesticated is the honeybee. -  Erika Engelhaupt

Jody Hewgill

In Kukekova's early visits, about 70 percent of the tame foxes were considered "elite," aquiver with excitement when people came around. The rest of the tame ones "didn't mind if you petted them, but they weren't super excited to interact with you," she says. Now, almost every tame fox is in the super-friendly elite group. (Foxes bred to be aggressive, on the other hand, are definitely not happy to have people around, much like the fearful rats Cagan encountered at the institute.)

Even though the friendly Novosibirsk foxes are genetically tame - some are sold as pets - not everyone would call the animals domesticated. "In an apartment, they would probably be very difficult pets," Kukekova says. The foxes have a strong odor, are more active at night and they aren't easily house-trained. The combination of living with people plus inherited changes in the foxes' genomes may eventually make them fully domesticated, but they aren't there yet.

Researchers have set out several biological criteria that should determine when silver foxes, or other animals, cross the line that divides merely tame from fully domesticated. Number one: Domesticated animals are genetically distinct from their wild forebears, and they inherit their human-friendly demeanor. That's different from wild animals that have been tamed but don't pass on that tameness to the next generation.

Two: Domestication makes animals dependent on humans for food and, for the most part, reproduction. Three: Breeding with wild counterparts becomes difficult, if not impossible. For example, domesticated plants don't drop their seeds when ripe; they rely on humans to spread their progeny. Finally, domesticated animals and plants should bear the physical hallmarks of domestication syndrome, such as a smaller skull for animals, and a narrower footprint for plants.

By these criteria, some people argue that cats - popular pets worldwide - are not fully domesticated. Cats probably started taming themselves about 9,500 years ago by hunting vermin, infesting early farmers' grain stores and feasting on food scraps. Farmers brought the mousers with them from the Middle East into Europe around 6,400 years ago, researchers reported June 19 in Nature Ecology & Evolution (SN Online: 06/19/17). But cats may not have been purring lap pets at that time, say molecular biologists Thierry Grange and Eva-Maria Geigl of the Institute Jacques Monod in Paris. That behavioral transformation may have happened later, perhaps in Egyptian cats that were quickly dispersed by boat around the ancient world.

In fact, cats haven't changed much physically or genetically from their African wildcat ancestors ( Felis silvestris lybica), Grange and Geigl say. Many felines still choose their own mates and hunt for food. Cats' famed aloofness may be another clue that their domestication isn't fully complete. Certainly, cats are more like their wild ancestors than dogs are, says Grange. But modern kitties are no longer wild cats, Geigl argues: "These couch potatoes are domesticated."

Taming the wild

Dogs appear to have been the first species domesticated by humans, followed by many others in Asia and the Middle East. As people spread to the New World, they continued to domesticate animals. Some were domesticated more than once in different locations.

T. TIBBITTS

Sources: D.E. MacHugh et al/Annu. Rev. Anim. Biosci. 2017; M. Germonpré et al/J. Archaeol. Sci. 2009

Relationship status

Bonds between humans and their animal companions may be more important than rigid biological criteria, Larson and other researchers argue. Domestication, says zooarchaeologist Alan Outram of the University of Exeter in England, "is best looked at with a more cultural definition."

Domestication is a gray area encompassing the point at which a hunter stops being interested in simply killing and eating an animal and starts being interested in controlling the animal, Outram says. The process probably starts slowly, first with animal herding and other forms of husbandry, such as controlling an animal's food supply and movement, culling at specific ages and directing breeding. When people start using animals, such as horses, for labor, riding or milking (fermented horse milk is a staple in parts of Central Asia), the animals "start moving to being culturally domestic," he says.

Newfound furry friend

Many domestication stories have vague beginnings, but we know exactly when the Syrian golden hamster, now a popular pet, first came under human control. On April 12, 1930, zoologist Israel Aharoni had workers dig up a mother hamster and her 11 babies spied by a farmer in his wheat field near Aleppo, Syria. Aharoni wanted a convenient animal to rear in the laboratory, but the creatures were so easily tamed that breeders began selling them as pets. Now, more than a million hamsters, descended from that first litter, run in wheels and transparent balls in homes across the United States. -  Erika Engelhaupt

Outram has evidence that the Botai people, hunter-gatherers that lived in Central Asia, were milking and bridling horses about 5,500 years ago (SN: 3/28/09, p. 15). "I certainly wouldn't want to make the argument that at the Botai time you've got anything like modern domesticated horses," he says. It was "more like equine husbandry and herding."

Scientists have to be careful not to judge how domestication happened in the past by the way animals are treated in modern Western cultures, says evolutionary biologist Ludovic Orlando of the University of Copenhagen. On a trip to collect DNA samples from ancient horse bones in Mongolia, Orlando got a whole new perspective on domestication.

"It completely changed my view of horse domestication, because I saw people interacting with this animal in ways I couldn't imagine myself," Orlando says. In Mongolia, horses roam free and their owners catch them, as needed, for riding or milking. "Once you've seen that, you can't think that domestication is just about parking animals somewhere. It's about the process of interacting with them and developing a relationship with them."

Dog days

If it's hard to pinpoint what domestication means in foxes tamed in controlled experiments, consider how difficult it is to decide whether the bones of a long-dead animal are from a wild or domesticated critter. That's the task of paleontologist Mietje Germonpré of the Royal Belgian Institute of Natural Sciences in Brussels, who studies dog domestication. The beloved pets are the subjects of much domestication research.

Scientists used to think that dogs were domesticated toward the end of the Ice Age, about 14,000 years ago (SN Online: 7/22/10). Germonpré and colleagues have studied skulls and jawbones of even more ancient canids in caves and other places where Ice Age people lived more than 25,000 years ago. One skull, found in a Goyet cave in Belgium, may be one of the oldest dogs ever discovered - or at least the oldest wolf that looked like a dog. At 36,000 years old, the Goyet pooch pushed dog domestication back to well before glaciers reached their peak coverage of the Northern Hemisphere.

Those early dogs may have been used as pack animals to move mammoth carcasses from hunting grounds to living quarters, says Germonpré. Big dogs may have helped humans hunt dangerous carnivores, such as cave bears, hyenas and cave lions. It's also possible the animals were used for fur or meat.

Fruit for a king

The ancestor of today's enormous, fleshy sweet watermelons was a surprisingly small, hard and bitter melon with pale green flesh. Just where this fruit was first grown is debated - all that's agreed on is that it was somewhere in Africa. An image of a watermelon appears in an Egyptian tomb dating to at least 4,000 years ago, and five watermelon seeds were found in King Tut's tomb. It's thought that the Egyptians bred the fruit as a tasty, and portable, water supply. -  Erika Engelhaupt

Germonpré's assertion that the Goyet dog is in fact a dog comes from comparing its skull and jaws with those of wolves and modern dogs. Most domesticated mammals, including dogs, tend to have smaller bodies than their wild counterparts, with smaller skulls that have shorter, wider snouts and shorter, lower jaws. Those features make adult dogs look more puppylike than grown wolves do. That type of facial remodeling is part of the domestication syndrome, which also includes curly tails, floppy ears and other characteristics common among domesticated animals but not wild ones. By Germonpré's measurements, the Goyet skull more closely resembles modern dogs than it does ancient or modern wolves.

She also has evidence of early dogs in Russia and the Czech Republic dating to 25,000 years ago or more. Other groups have reported data suggesting that a 33,000-year-old canid from the Altai Mountains of Russia was also an early dog.

Other researchers disagree, saying the animals were really wolves. Three-dimensional reconstructions of the skulls of the Goyet dog and another Ice Age dog show that the animals' snouts didn't angle from the skull the way modern dogs' do, and the ancient versions didn't have some other features of modern dogs (SN Online: 2/5/15).

Larson says he's not bothered that the Goyet hound didn't physically measure up in the 3-D study. The canid may have behaved very much like a dog and had close ties to humans. Those early dogs didn't have thousands of years of intense breeding selection to sculpt them into the image of modern dogs. Even modern dogs have been transformed dramatically in just 200 to 300 years of breeding (SN Online: 4/26/17; SN: 1/31/09, p. 26). "What was a dog 15,000 to 30,000 years ago is not what a dog is now," Larson says.

V. Pitulko and A. Kasparov/Journal of Archaeological Science: Reports 2017

The timing of Fido's taming isn't the only dispute. Researchers also wrangle over where and how many times it happened. Dueling genetic studies based on the DNA of modern dogs and wolves suggest the fellowship between humans and dogs could have been forged in the Middle East, Central Asia, East Asia or, as Goyet's archaeological evidence suggests, in Europe. Research reported by Larson and colleagues last year in Science suggests that dog domestication happened at least twice, once in Europe and once in East Asia (SN: 7/9/16, p. 15).

DNA evidence indicates that the Goyet dog and the 33,000-year-old Russian dog are not the ancestors of today's dogs or wolves (SN: 12/14/13, p. 6). Scientists examined mitochondrial DNA, which is passed from mothers to offspring, to trace maternal lineages of ancient and modern dogs and wolves. The mitochondrial DNA of the Goyet and Russian dogs belongs to a maternal lineage that didn't leave any modern descendants, researchers reported in Science in 2013. But it doesn't mean the animals weren't on the way toward being domesticated, Germonpré says.

Perhaps those dogs were part of an early, failed attempt at domestication, she says. "The domesticated animals became extinct, and domestication started up again somewhere else."

Rice story shattered

Locating the cradle of most species' domestication is difficult. Many were domesticated before writing was even invented. So scientists have to extract the story from artifacts and bones or from DNA.

The origin of Asian rice has been hotly debated for many years. Scientists used to think modern rice, Oryza sativa, was domesticated twice: sticky, short-grained japonica rice was domesticated in China, and in India, rice was domesticated into long-grained varieties indica and aus. Archaeological finds suggest that rice cultivation started about 9,000 years ago in China and 8,000 years ago in India. But true domestication probably happened only once - in China, says Dorian Fuller, an archaeobotanist at University College London.

People were certainly cultivating rice in India, but that's just one step in the domestication process. The final threshold that separates a fully domesticated crop from a cultivated one is that domesticated plants require human intervention to spread their seeds, Fuller says. Wild grains, for instance, "shatter" their seed heads when ripe. But domesticated grains, including rice, wheat, barley, sorghum and millet, have mutations that prevent shattering. The only way the grain crops can propagate is if humans collect and plant the seeds.

On the backs of llamas

Though the Inca built great cities and had a sophisticated understanding of astronomy, they didn't use wheels to transport goods. Instead, llamas carried the heavy loads along the empire's vast road system. And llama dung fertilized Inca fields, possibly helping to grow maize at high altitudes. South America's llamas and alpacas are domesticated versions of two wild camel species: guanaco (ancestor of llamas) and the smaller vicuña (alpacas' ancestor). The earliest evidence of the animals' domestication is from bones found at archaeological sites in the Peruvian Andes, dating to at least 6,000 years ago. -  Erika Engelhaupt

It may have taken nearly 2,000 years for people in China's Yangtze River basin to wrest complete control over rice, researchers reported last year in Scientific Reports. Scientists examined rice fossils to determine how easily the plant shattered its seed. Although people were growing an early rice 9,000 to 8,400 years ago, about 60 percent of plants were still dispersing seeds via shattering. It wasn't until about 7,000 to 6,500 years ago that nonshattering rice began to edge out shattering varieties.

By examining DNA from modern rice strains, Fuller and evolutionary geneticist Michael Purugganan of New York University think they've pieced together the rest of the rice domestication story. DNA evidence clearly shows that China's wild O. rufipogon was domesticated into O. sativa japonica. Traders carried domesticated japonica from China to India, where it was bred with the cultivated rice species O. nivara to produce domesticated aus about 4,000 years ago, Fuller, Purugganan and colleagues reported in January in Molecular Biology and Evolution. Indica's story is less clear because its cultivated predecessor in India is still unknown. But the genetic evidence indicates that it got its domestication genes from China's japonica.

Tails (and feathers) from the past

Working out the step-by-step history of domesticated animals is just as complicated. Until recently, researchers compared DNA from modern domestic animals with that of wild relatives, preferably the wild species that gave rise to the domesticated species. Sometimes that's impossible to do. There are no wild cattle, for instance. Aurochs - massive cattle that eventually gave rise to domesticated cows - went extinct when the last one died in 1627 in Poland's Jaktorów Forest.

Horses' wild ancestors are also extinct, but remains from the warrior steeds of Genghis Khan and medieval knights, the Romans' chariot horses and the mounts of the ancient Scythians, Greeks and Persians might fill in gaps in horse history and prehistory. Through the Pegasus project, begun in 2015, Orlando and colleagues have collected ancient DNA from horse fossils from a wide variety of time periods and cultures. "We're looking at every possible ancient equine culture on the planet," Orlando says.

Before the project, scientists mostly had to rely on DNA from modern horses to piece together the story of how the beasts of burden were domesticated. Findings of those studies may be misleading, Orlando and colleagues have concluded. For instance, studies of modern horses' mitochondrial DNA plus Y chromosomes (passed from fathers to sons) told a nice, neat story: At the beginning of horse domestication, people must have captured just a few stallions and bred those stallions to many different mares.

Eric Crubézy

But when Orlando and colleagues examined DNA of ancient horses, they found that the story started completely differently. Domesticated horses living 2,300 to 2,700 years ago - about the midpoint of horse domestication - had a wide variety of Y chromosomes, the researchers reported April 28 in Science (SN: 5/27/17, p. 10). That means many stallions contributed DNA to horses' gene pool for at least the first few thousand years of domestication. It wasn't until sometime after 2,300 years ago that people started winnowing down the number of stallions that were allowed to breed. Orlando doesn't know yet when most Y chromosomes were lost.

The story of chicken domestication is being retold as well, also thanks to DNA evidence. Modern chickens carry a version of the thyroid-stimulating hormone receptor gene, TSHR, that has been linked to several domesticated chicken characteristics: year-round egg laying, faster egg production at sexual maturity, reduced aggression toward other chickens and less fear of people. Because that version of the gene is ubiquitous in present-day chickens and is responsible for those attractive traits, researchers thought that people probably selected the most prolific egg layers right from the very beginning, about 4,000 years ago. Picking better laying hens would also mean unwittingly choosing the domesticated version of TSHR.

But, the egg-laying version of the gene didn't become popular among chickens in Europe until about A.D. 920, around the time that Christians started giving up meat on fasting days in favor of fish and fowl, Larson and colleagues reported May 2 in Molecular Biology and Evolution. (Rabbit domestication followed a religious proclamation, as well. In 600, Pope Gregory I declared that fetal rabbits, called laurices, are aquatic, which made them fish, suitable to eat during Lent. Rabbit breeding took off in monasteries in southern France, and bunnies quickly became domesticated.)

Titanic turkeys

Turkeys are one of the most recently domesticated animals. In 2016, researchers found 1,500-year-old turkey eggs plus bones of both chicks and adult birds in the Oaxaca region of Mexico. The presence of turkeys at all life stages suggests they were being raised as food. They may have been important symbolically too; remains have been found buried alongside humans. The birds have changed a great deal since those early days: Some commercially bred turkeys have breast muscles so large that the birds can't get close enough to mate. Humans must artificially inseminate them, a sign of true domestication. -  Erika Engelhaupt

If Larson's calculations are correct, egg laying wasn't the main criterion for selecting which chickens to keep until the Middle Ages. By that time, the birds had been domesticated for thousands of years. So what were ancient people looking for when striking up friendships with the feathered animals - or any other creatures? Many people think it was about the relationship; tameness and docility were the most attractive qualities in potential animal pals. It's hard to be buddies with a creature that constantly runs from you, or worse, attacks.

Docility makeover

A breeding experiment with wild red jungle fowl, the precursor to the domesticated chicken, may help explain whether selecting for tameness is the triggering event of domestication and all its characteristics. Behavioral geneticist Per Jensen of Linköping University in Sweden is in the middle of a domestication redo. He and colleagues have bred eight generations of the rust-feathered birds. Like the rats, mink and foxes in Novosibirsk, Jensen's jungle fowl are bred to be more (or less) fearful of humans than their ancestors were.

From the beginning, the researchers took great pains to select birds only for their behavior: Jungle fowl were tested for tameness at 12 weeks old, before they reached sexual maturity. One researcher would approach the fowl and attempt to touch it, while an outside observer scored the bird's reaction. Neither researcher knew whether they were testing a jungle fowl from the tame or fearful line.

"Mind you, this went well for two or three generations but then the difference started to be so big it was difficult to keep a secret," Jensen says. After that, the tame birds were so calm they didn't react when a human entered the room. "You basically had to kick them out of your way," he jokes. By the sixth generation, tame birds were bigger and had a higher metabolism than their fearful counterparts, Jensen and colleagues reported in Biology Letters in 2015. Changes in body size, reproduction and metabolism happened quickly, even though the researchers were only choosing birds for tameness.

The tame birds, Jensen says, "show a lot of traits that you really associate with domesticated animals, but I'm not sure anyone would accept that," he says. Becoming what other people think of as domesticated chickens may take more time: jungle fowl hens that lay eggs year-round and are big enough to eat. "I don't think we're talking about hundreds of generations, maybe dozens. It's a much faster process than we used to think."

Again and again, animals of various species domesticated at different times in different parts of the world develop the same domestication syndrome characteristics: more extensive breeding periods; smaller brains, hearts and teeth; small or floppy ears; spotted coats; curly hair and tails; variable numbers of vertebrae in the spine; and juvenile faces with shorter snouts. Researchers have found evidence that pigmentation genes differ between domestic and wild animals. Others have pinpointed changes in brain chemistry or genes involved in face development that may separate tame and wild animals. But scientists didn't have a unifying explanation for why the physical traits of domestication syndrome were linked to tameness until three years ago.

Choices and changes

Humans may have selected animals for tameness (left column), with those choices leading to unintended features seen in many domesticated species (right column). One hypothesis is that tameness, which involves a calmer nervous system and a dampened stress hormone response, results from alterations in neural crest cells. Those cells migrate throughout the embryo to form many tissues. Changes in the cells' migration might account for many physical traits linked to tameness in domesticated animals.

Selection for tameness

Selected traits

Common unselected traits

Less reactive, reduced stress, less fear of humans. Tameness occurs because:

- Adrendal glands produce less adrenaline and noradrenaline, the fight-or-flight hormones

- Nervous system is less sensitive

White patches in coats due to fewer pigment-producing cells

Juvenile feathers - facial bones are sculpted differently and cartilage softens, leading to smaller teeth and jaws, shortened snout and floppy ears

Smaller forebrain

Source: A.S. Wilkins, R.W. Wrangham and W.T. Fitch/Genetics 2014

That's when geneticist Adam Wilkins of Humboldt University of Berlin, primatologist Richard Wrangham of Harvard University and evolutionary biologist and cognitive scientist W. Tecumseh Fitch of the University of Vienna introduced a new hypothesis. Selecting animals for tameness, they said, could alter genes that control a group of developmentally important cells called neural crest cells. Those embryonic cells migrate in the embryo and contribute to tissues involved in the fight-or-flight response, facial development and coloring.

Choosing animals for tameness might be selecting for ones that have changes in how their neural crest cells function, the researchers proposed in Genetics in 2014 (SN: 8/23/14, p. 7). Calmer domesticated animals might have neural crest cells that move or work differently than the cells in more fearful wild animals. Because neural crest cells contribute to so many tissues in the body, altering their function could change an animal's behavior, appearance and biology, the researchers reasoned. For the first time, domestication researchers had a hypothesis about the link between tameness and physical traits that could really be put to the scientific test.

Not much of a mouthful

It would be hard to recognize today's toothsome corncobs from the plant's wild progenitor, a grass called teosinte. When Native Americans began domesticating teosinte, its ears were two or three inches long, holding a sparse five to 12 kernels each. In fact, teosinte looks so different from maize that scientists questioned the link, first proposed in the 1930s, until genetics could prove it more than half a century later. In 2009, archaeologists found the earliest known evidence of domesticated maize at an 8,700-year-old site in southwestern Mexico, alongside stone tools used to grind the plants. -  Erika Engelhaupt

Since the neural crest hypothesis surfaced, geneticists have found tantalizing clues that Wilkins, Wrangham and Fitch are onto something. Analysis of cat DNA found that house cats and wild cats have different versions of genes implicated in neural crest cell migration (SN: 12/13/14, p. 7). When Orlando and colleagues examined horse DNA for genes that may have rapidly changed during domestication, they too found genes involved in neural crest cell function.

While at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, Cagan compared DNA from the tame rats and mink at Novosibirsk, and from other domesticated species, with DNA from aggressive counterparts and wild ancestors. In unpublished research, Cagan (now at the Wellcome Trust Sanger Institute in Hinxton, England) found that genes involved in helping neural crest cells migrate differed between the tame and wild animals (SN: 6/13/15, p. 11). That might explain the white patches of fur, shorter snouts and curly tails of the tame animals.

Jensen calls the neural crest cell hypothesis "a very speculative idea that may not be applicable across species." He is looking more closely at the neural crest in the jungle fowl. He and colleagues are collecting eggs to track the cells' movements in tame and fearful birds. Even if the researchers find differences, he says, "we still need to find the genetic mechanisms that are causing the neural crest cells to act as they do."

Larson expects many revelations in the next year or two about when, where and how domestication happened. "Even the big themes are going to be radically revised," he says. Domestication is likely to be a far more complicated process than researchers expected, but Larson hopes people will find it all the more interesting for its lack of simplicity. "We want to get people to embrace the ambiguity and to love the complexity."

This article appears in the July 8, 2017, issue of Science News with the headline: "The road to tameness: Fresh ideas emerge about the origins of humans' relationships with their favorite species."

Questions or comments on this article? E-mail us at feedback@sciencenews.org

A version of this article appears in the July 8, 2017 issue of Science News.

Citations

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J. Y. Choi et al. The Rice Paradox: Multiple origins but single domestication in Asian rice. Molecular Biology and Evolution. Vol. 4, January 12, 2017, p. 969. doi: 10.1093/molbev/msx049.

C. A. Driscoll, D. W. Macdonald and S. J. O'Brien. From wild animal to domestic pets an evolutionary view of domestication. Proceedings of the National Academy of Sciences. Vol. 106, June 16, 2009, p. 9971. doi:10.1073pnas.0901586106.

D. E. MacHugh, G. Larson and L. Orlando. Taming the Past: Ancient DNA and the study of animal domestication. Annual Review of Animal Biosciences. Vol. 5, February 2017, p. 329. doi: 10.1146/annurev-animal-022516-022747.

M. Germonpré et al. Palaeolithic and prehistoric dogs and Pleistocene wolves from Yakutia: Identification of isolated skulls. Journal of Archaeological Science. Vol. 78, February 2017, p. 1. doi:10.1016/j.jas.2016.11.008.

M. Germonpré, M. Lázničková-Galetová and M. V. Sabin. Palaeolithic dog skulls at the Gravettian Předmostí site, the Czech Republic. Journal of Archaeological Science. Vol. 39, January 2012, p. 184. doi: 10.1016/j.jas.2011.09.022.

M. Germonpré et al. Fossil dogs and wolves from Palaeolithic sites in Belgium, the Ukraine and Russia: osteometry, ancient DNA and stable isotopes. Journal of Archaeological Science. Vol. 36, February 2009, p. 473. doi: 10.1016/j.jas.2008.09.033,

N. D. Ovodov et al. A 33,000-year-old incipient dog from the Altai Mountains of Siberia: Evidence of the earliest domestication disrupted by the Last Glacial Maximum. PLOS ONE. Vol. 6, July 28, 2011, p. e22821. doi:10.1371/journal.pone.0022821.

A. S. Druzhkova et al. Ancient DNA analysis affirms the canid from Altai as a primitive dog. PLOS ONE. Vol. 8, March 6, 2013, p. e57754. doi: 10.1371/journal.pone.0057754.

L. A. F. Frantz et al. Genomic and archaeological evidence suggests a dual origin of domestic dogs. Science. Vol. 352, June 3, 2016, p. 1228. doi: 10.1126/science.aaf3161.

O. Thalmann et al. Complete mitochondrial genomes of ancient canids suggest a European origin of domestic dogs. Science. Vol. 342, November 15, 2013, p. 871. doi: 10.1126/science.1243650.

P. Librado et al. Ancient genomic changes associated with domestication of the horse. Science. Vol. 356, April 28, 2017, p. 442.

L. Loog et al. Inferring allele frequency trajectories from ancient DNA indicates that selection on a chicken gene coincided with changes in medieval husbandry practices. Molecular Biology and Evolution. May 2, 2017. doi:10.1093/molbev/msx142.

A. G. Drake, M. Coquerelle and G. Colombeau. 3D morphometric analysis of fossil canid skulls contradicts the suggested domestication of dogs during the late Paleolithic. Scientific Reports. Vol. 5, February 5, 2015, p. 8299. doi: 10.1038/srep08299.

B. Agnvall et al. Is domestication driven by reduced fear of humans? Boldness, metabolism and serotonin levels in divergently selected red junglefowl (Gallus gallus). Biology Letters. Vol. 11, September 16, 2015. doi: 10.1098/rsbl.2015.0509.

A. S. Wilkins, R. W. Wrangham and W. T. Fitch. The "domestication syndrome" in mammals: A unified explanation based on neural crest cell behavior and genetics. Genetics. Vol. 197, July 1, 2014, p. 795. doi: 10.1534/genetics.114.165423.

M. R. Sánchez-Villagra, M. Geiger and R. A. Schneider. The taming of the neural crest: a developmental perspective on the origins of morphological covariation in domesticated mammals. Royal Society Open Science. Vol. 3, June 1, 2016, p. 160107. doi: 10.1098/rsos.160107.

Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master's degree in science journalism from Boston University.

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DNA evidence is rewriting domestication origin stories

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O ne lab full of rats looks pretty much the same as another. But visiting a lab in Siberia, geneticist Alex Cagan can distinguish rats bred to be tame from those bred to be aggressive as soon as he opens the lab door. "It's a completely different response immediately," he says.

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Lactose intolerance proved deadly during periods of European famine for its symptoms of malnourishment. But even with the increased usage of milk products, resistance/ tolerance wasn't common until 3,000 years ago.

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Ancient Europeans may have evolved an ability to digest milk thanks to periodic famines and disease outbreaks.

Europeans avidly tapped into milk drinking starting around 9,000 years ago, when dairying groups first reached the continent's southeastern corner, researchers report July 27 in Nature. Yet it took several thousand years before large numbers of Europeans evolved a gene for digesting lactose, the sugar in milk, the investigators say.

These discoveries - based on animal fat residue samples from hundreds of archaeological sites and a trove of DNA data - undermine an influential idea that milk use dramatically increased as the product's nutritional and health benefits drove the evolution of lactose tolerance, say biogeochemist Richard Evershed of the University of Bristol in England and colleagues.

Milk drinkers who can't digest lactose experience diarrhea, gas, bloating and intestinal cramps. Those uncomfortable reactions were too mild to move the evolutionary needle toward lactose tolerance on their own, Evershed's group says. But during periodic famines and infectious disease outbreaks, lactose-induced diarrhea became fatal for severely malnourished individuals in farming communities, the scientists suggest. Those recurring threats hotwired the evolution of lactose tolerance, they contend.

Evershed's report "comprehensively rules out" widespread milk consumption as the evolutionary force behind lactose tolerance, says bioarchaeologist Oliver Craig of the University of York in England. Further research needs to clarify the scale and extent of famines or infectious disease episodes that may have influenced how ancient Europeans digested milk, adds Craig, who did not participate in the new study. Investigators must also keep in mind that cheese and other low-lactose dairy products date to as early as around 7,400 years ago in Europe ( SN: 12/12/12). If these foods were widely available, it's unclear why lactose intolerant Europeans would not have survived times of famine or disease, Craig says.

Evershed's team mapped estimated frequencies of milk use across Europe from around 9,000 to 500 years ago by analyzing previously published data from animal fat residues extracted from more than 13,000 pottery fragments at about 550 archaeological sites.

At the beginning of that time span, migrating farmers introduced dairying to southeastern Europe's Balkan Peninsula, where residents embraced regular milk drinking, the investigators say. Milk use then fluctuated over time in different parts of the continent. After about 7,500 years ago, relatively heavy milk use characterized western France, northern Europe and the British Isles. Dairying occurred less often in central Europe.

Evershed's team also tracked the emergence and spread of the main gene responsible for lactose tolerance using published ancient DNA data from nearly 1,800 Europeans and Asians. The earliest European evidence of a gene variant in adults responsible for boosting the activity of lactase, an enzyme that confers tolerance by chemically breaking down lactose, dates to about 6,650 years ago, the researchers say. But this trait, known as lactase persistence, did not become common in Europe until around 3,000 years ago, they find.

Before that time, increasing levels of lactase persistence tended to align with population busts linked to famines in particular regions, the researchers report. Between 8,000 and 4,000 years ago, excavated farming sites across Europe display signs of periodic population declines that were influenced by severe food shortages, the researchers say ( SN: 10/1/13).

Estimates of settlement density, a measure of how closely together people lived, also tended to decline at times of increasing lactase persistence. The spread of animal-borne infections such as salmonella lowered settlement densities as residents unable to digest lactose suffered an excess of deaths, the scientists suspect. In those periods of malnourishment and illness, lactase persistence boosted access to badly needed nutrients in milk, Evershed's group speculates.

But archaeologist Ron Pinhasi of the University of Vienna is not convinced the famine and disease theory holds up. Diarrhea causes death more often in malnourished children, he says, so he questions whether it would have led to enough adult fatalities to trigger the evolution of milk tolerance. No current proposal explains how lactase persistence spread, he says.

In other parts of the world, and for equally mysterious reasons, regular milk consumption doesn't necessarily stimulate the spread of lactose tolerance. For instance, lactose tolerance rarely occurs among milk-drinking Central Asian herders but biological signs of lactose tolerance often appear in East African Hadza hunter-gatherers, who don't drink milk.

Questions or comments on this article? E-mail us at feedback@sciencenews.org

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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Famine and disease may have driven ancient Europeans' lactose tolerance

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Ancient Europeans may have evolved an ability to digest milk thanks to periodic famines and disease outbreaks. Europeans avidly tapped into milk drinking starting around 9,000 years ago, when dairying groups first reached the continent's southeastern corner, researchers report July 27 in Nature.

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Weathering of bones is a typical practice to determine the age of remains. However, a scientist has been using proteins and other molecules to have an objective way to clock the time of death.

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Carolyn Wilke is a freelance science journalist based in Chicago and former staff writer at Science News for Students. She has a Ph.D. in environmental engineering from Northwestern University.

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One forensic scientist is scraping bones for clues to time of death

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The bones of more than 100 cadavers are shedding light on a more precise and reliable way to determine when someone died.

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When participants consumed any of the four sugar substitutes, their gut bacteria profile changed during the two weeks of intake. What causes the sugar substitutes to change gut bacteria?

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As Diet Coke and its sweetener aspartame wrap up 40 years or so on American store shelves, the decades-long controversy around the safety of sugar substitutes continues. Ever since diet drinks hit the stores in the 1950s, rumors have swirled that such sweeteners-which today also include saccharin, sucralose and stevia-do more than satisfy a sweet tooth without the calories of sugar. But whether that "more" exists hasn't been easy to establish.

In a new study of four sugar substitutes, researchers found that these nonnutritive sweeteners don't just travel through the body unnoticed. The study results, published on August 19 in Cell, link two of the sweeteners-saccharin and sucralose-to spikes in glucose levels and suggest all four are tied to a shift in gut microbe profiles. Whether these findings translate into trouble, benefit or neither remains to be seen, and aficionados of diet drinks don't need to trash the diet soda can just yet.

"It's cool science and was very well designed, thought out and executed," says Dylan Mackay, an assistant professor of nutrition and chronic disease at the University of Manitoba, who was not involved in the study. "I've always wanted to do these more at-home trials, and they were able to pull it off in a really interesting way."

In 2014 researchers found a link between microbiome changes and blood glucose responses in mice after intake of sugar substitutes. To see if those same links applied to humans in the new study, the scientists selected participants from a potential pool of more than 1,375people, ruling out anyone who consumed noncaloric sweeteners in their regular daily life. Some had unknowingly done so by way of protein powders, chewing gum, or low-sugar snacks or desserts.

The researchers split the final 120 participants into six groups of 20. In four of these groups, participants consumed commercial packets of one of the four sweeteners at levels below their federal daily limit. A fifth group consumed only the filler used in these packets, which is commonly added to bulk out the tiny amount of sugar substitute they contain. The sixth group had no intervention.

During the two weeks that participants consumed their assigned sweetener or the filler, they also took oral glucose tolerance tests, which are used to measure the body's response to sugar and can be employed to diagnose some forms of diabetes. For these tests, they drank a glucose solution every morning after overnight fasting and used home-based continuous glucose monitors to track their blood glucose levels. The researchers also collected oral and stool samples from the participants to analyze the species of microbes they hosted. Study investigators additionally measured levels of some products of metabolism in the blood.

The participants who consumed saccharin or sucralose had a steeper blood glucose response than any of the other groups. When participants consumed any of the four sugar substitutes, their gut bacteria profile changed during the two weeks of intake. Along with these changes, levels of the metabolic products changed, too. For example, in participants who took saccharin, the production of a type of amino acid increased,echoing patterns seen in people with diabetes.

To confirm a link between microbial profiles and blood glucose responses, the investigators orally administered microbiomes-taken from the human participants with the highest and lowest blood glucose spikes following sweetener consumption-to germ-free mice. Mice exposed to microbiomes from human "top responders" showed changes in their blood glucose that "very significantly mirrored those of the donor individuals," says study author Eran Elinav, principal investigator of the Host-Microbiome Interaction Research Group at the Weizmann Institute of Science in Rehovot, Israel, and director of the Microbiome and Cancer Division at the German National Cancer Center in Heidelberg.

This part of the work "is a really cool portion of the paper," Mackay says. The findings in mice "are interesting mechanistic evidence that maybe [these sweeteners] are having an effect."

The effects of the sweeteners on blood glucose are likely highly personalized, Elinav says. But the results suggest these compounds don't just pass through the body, as some originally thought.

Part of the personalized response will relate to the health of the person involved, Mackay says. The findings "can't extend to people who may be overweight or have obesity or impaired glucose tolerance or type 1 or type 2 diabetes," he says.

The findings don't settle the question of whether any effects will be meaningful for human health-a subject to tackle in other studies, Elinav says. The researchers also don't know if these effects will persist beyond the two weeks of exposure in the current study, Mackay says.

The study involved healthy people without overweight or obesity and who represent only a subset of the population that consumes food and drink with these sugar substitutes, Mackay notes. "From a user perspective, as someone with type 1 diabetes, almost everything I use has aspartame," he says. "I'm not going to stop that and switch back to regular glucose or sugar-containing products because of these results."

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Some Sugar Substitutes Affect Blood Glucose and Gut Bacteria

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As Diet Coke and its sweetener aspartame wrap up 40 years or so on American store shelves, the decades-long controversy around the safety of sugar substitutes continues. Ever since diet drinks hit the stores in the 1950s, rumors have swirled that such sweeteners-which today also include saccharin, sucralose and stevia-do more than satisfy a sweet tooth without the calories of sugar.

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Researchers conducted a study and found no correlation between high perceived growth scores on the standard inventory and actual growth scores on the modified inventory and five surveys related to well-being. Wouldn't a persons ability to grow after a traumatic experience be different for each person? Wouldn't some people handle situations in different ways resulting in different outcomes?

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"What does not kill me, makes me stronger," 19th century German philosopher Friedrich Nietzsche famously wrote. Variations of that aphorism abound in literary, spiritual and, more recently, psychological texts.

That psychological research suggests that at least half of survivors not only recover from traumatic experiences but also go on to develop more appreciation for life, stronger relationships and emotional strength - a phenomenon researchers call "posttraumatic growth."

The idea that bad events can often lead to good outcomes is appealing, especially in this present and difficult moment. More than 6.3 million people worldwide have died from COVID-19, and deaths continue to mount ( SN: 5/18/22). Russia's invasion of Ukraine has surpassed a hundred days ( SN 4/12/22). And a recent string of mass shootings - including at a July 4 parade in Highland Park, Ill., an elementary school in Uvalde, Texas, and a grocery store in Buffalo, N.Y. - has left U.S. communities reeling ( SN: 5/26/22).

But in a series of talks presented in May in Chicago at the Association for Psychological Science conference, some researchers called findings of posttraumatic growth "largely illusory." Growth studies suffer from serious methodological flaws, these researchers say. That includes a reliance on surveys that require people to assess their personal growth over time, a task that most people struggle with.

Better research tools may not remedy the problem. That's because these studies are fundamentally flawed, the researchers say. They argue that the impetus to study trauma in terms of growth stems from a Western mind-set that tends to value positive emotions and devalue or even avoid negative emotions ( SN: 12/7/19). That can pressure survivors to deny or suppress their negative feelings, which could have harmful consequences.

That yearning for positive outcomes can create "toxic cultural narratives," says personality psychologist Eranda Jayawickreme of Wake Forest University in Winston-Salem, N.C. Referring to parents who lost a child in the Uvalde mass shooting, he says: "There is something grotesque about this expectation that people could come back from something like this."

Focusing on the good

A half-century ago, psychologists largely treated a person's difficulty in rebounding from traumatic events as a personal failing. But research on returning Vietnam War veterans and other trauma survivors began shifting that way of thinking. In 1980, the American Psychiatric Association created a category for posttraumatic stress disorder, or PTSD, in its manual of mental disorders. Those struggling with the disorder might experience flashbacks, nightmares and severe anxiety.

"Thirty years ago, everyone was focused on the worst outcomes," says trauma and resilience expert George Bonanno of Columbia University.

But only about one-fifth of people who experience trauma develop PTSD, psychologists realized. In the mid-1990s, psychologists Richard Tedeschi and Lawrence Calhoun, both then at the University of North Carolina at Charlotte, wrote in the 1996 Journal of Traumatic Stress that a focus on suffering obscured the good that can emerge from trauma.

The pair developed a now widely used "growth inventory" to assess positive outcomes that people reported after experiencing a traumatic event. In the 21-item survey, respondents rate statements such as "I have more compassion for others" and "I established a new path for my life." Respondents can choose from a score of 0 for "I did not experience this change as a result of my crisis" to 5 for "I experienced this change to a very great degree as a result of my crisis." The items reflect five broad categories: relating to others, personal strength, new possibilities, appreciation of life and spiritual change.

"Posttraumatic growth is you go down to the depths and then at some later point, rise above that baseline into some other realm," says Tedeschi, now the chair of Boulder Crest Institute for Posttraumatic Growth, an organization in Bluemont, Va., that uses research on posttraumatic growth to help combat veterans, first responders and their families.

Cracks in the theory

But some researchers soon began to question people's ability to accurately respond to the growth survey.

In a now-seminal 2009 study in Psychological Science, researchers recruited about 1,500 undergraduate students and tracked them for eight weeks. Once at the start of the study and once at the end, students responded to surveys for each of the five growth categories covered by the growth inventory, along with a modified version of the inventory.

Unlike Tedeschi and Calhoun's inventory, which asks respondents to compare their present state of mind to the past, the five surveys and modified inventory asked respondents to reflect on the present. For instance, in the relationship quality category, respondents rated the statement: "I enjoy personal and mutual conversations with family members or friends."

During that eight-week period, 122 students reported experiencing a traumatic event that caused high levels of distress. Those students also completed the standard growth inventory at the end of the eight weeks. The researchers found no correlation between high perceived growth scores on the standard inventory and actual growth scores on the modified inventory and five surveys related to well-being.

That mismatch occurs because people are terrible at remembering how they felt in the past, says study coauthor Crystal Park, a clinical health psychologist at the University of Connecticut in Storrs. "I want to throw out the concept of people being able to accurately report that they have grown."

Tedeschi counters that trauma cleaves one's life into a before and after, making it more feasible for many people to distinguish changes over time. What's more, growth takes time, he says. "You can't expect people to change their spiritual beliefs in eight weeks."

But how much time? And if enough time passes, how does one know that the growth arises from the trauma and not some other major life experience, like moving across the country or having children? Research shows that people are not great at introspection, Jayawickreme says. "We tend to come up with all types of stories for change, but those stories are just stories. They don't really reflect what actually caused that change."

'Pulling for growth'

Other problems come with the design of the original inventory, Jayawickreme and others argue. For example, the questions account for positive changes only, and the worst or lowest outcome a respondent can give is that they experienced no change as a result of their crisis. That framing puts pressure on survivors to report growth when they may feel worse, Jayawickreme says. "The items are pulling for growth."

Tedeschi and colleagues have recently developed a new growth survey that also accounts for negative changes following trauma. But it's not yet as widely used in research on posttraumatic growth as the original.

Meanwhile, in unpublished work, trauma researcher Adriel Boals of the University of North Texas in Denton sought to overcome what he sees as the original survey's growth bias in a different way. He asked people whether they changed because of a traumatic event, a measure of growth, or despite the event.

"Half the people are picking, 'I changed despite this event,'" Boals says. That suggests that people who may report growth on the original inventory do not actually attribute that growth to the trauma but to other life experiences.

What's more, say Jayawickreme and others, unlike most psychological surveys, which require respondents to complete a single cognitive task along the lines of "how are you doing now" or "reflect on the present," the original growth inventory requires four cognitive tasks. Respondents must consider how they are doing at the moment and how they were doing prior to the trauma. They then must compute that difference in well-being, as well as determine if the trauma, or some other life event such as aging or having a child, caused the change.

But people don't actually go through those steps. That finding was reported in March in Anxiety, Stress and Coping and at the May conference by Boals, Park and Elizabeth Griffith, a psychologist also at the University of North Texas.

When the team compared response times among college students taking the standard growth inventory with students taking a simplified version involving a single cognitive task, the researchers found that the students completing the standard inventory took just 8 percent longer than the other students. That equates to just a half-second longer response time per item, Boals says. "If you can go through steps 2, 3 and 4 ... in half a second, you're drinking stronger coffee than I am."

Avoiding negative emotions

Beyond the methodological particulars, some researchers studying trauma across cultures question some Western psychologists' focus on personal growth and, to a lesser degree, resilience - a phenomenon marked by stability during hard times, rather than a steep increase in well-being after an initial decline as observed in posttraumatic growth ( SN: 10/19/14).

"In Euro-American societies, 'resilience' and 'posttraumatic growth' are commonly used metaphorical terms for positive responses to extreme adversity," write University of Zurich psychologists Iara Meili and Andreas Maercker in 2019 in Transcultural Psychiatry. They attribute the popularity of these Western "metaphors" to individualistic societies' emphasis on self-determination and agency, even in the face of illness or death. These concepts exist elsewhere, Maercker says. But they rarely take on such outsize significance - what he calls "almost a religious approach."

A societal expectation of growth can put tremendous pressure on survivors to hide their suffering, Jayawickreme says.

Take, for instance, a study where researchers compared outcomes among about 380 Norwegian soldiers who deployed to Iraq in 2004. Soldiers who reported the most personal growth five months after returning home also reported the most posttraumatic stress symptoms 10 months later, researchers noted in 2015 in Clinical Psychological Science.

"Self-reports of posttraumatic growth should be highly correlated with doing well on other measurements, like less depression, more satisfaction with life, those types of things," says Boals, who was not involved with this research. "But if anything, [growth] is positively correlated with PTSD symptoms."

Ultimately, the most compassionate response to suffering is to validate survivors' feelings, Jayawickreme says. "How people respond to adversity is nuanced. People can change in positive ways. People can change in negative ways. People cannot change at all. And that's fine."

Questions or comments on this article? E-mail us at feedback@sciencenews.org | Reprints FAQ

Citations

R.G. Tedeschi and L.G. Calhoun. The posttraumatic growth inventory: Measuring the positive legacy of trauma. Journal of Traumatic Stress. Vol. 9, 1996, p. 455. doi: 10.1002/jts.2490090305.

A. Boals, E.L. Griffith and C.L. Park. Can respondents accurately report posttraumatic growth when coached through the required cognitive steps? Anxiety, Stress and Coping.Posted online March 10, 2022. doi: 10.1080/10615806.2022.2047949.

I. Meili and A. Maercker. Cultural responses on positive responses to extreme adversity: A playing field for metaphors. Transcultural Psychiatry.Vol. 56, October 2019, p. 807. doi: 10.1177/1363461519844355.

K. Taku et al. Posttraumatic growth (PTG) and posttraumatic depreciation (PTD) across ten countries: Global validation of the PTG-PTD theoretical model. Personality and Individual Differences, Vol. 169, February 2021, p. 110222. doi:10.1016/j.paid.2020.110222.

I.M. Englehard, M.J.J. Lommen and M. Sijbrandig. Changing for better or worse? Posttraumatic growth reported by soldiers deployed to Iraq. Clinical Psychological Science.Vol. 3, September 2015, p. 663. doi: 10.1177/2167702614549800.

P. Frazier et al. Does self-reported posttraumatic growth reflect genuine positive change? Psychological Science.Vol. 20, July 1, 2009, p. 912. doi: 10.1111/j.1467-9280.2009.02381.x.

Sujata Gupta is the social sciences writer and is based in Burlington, Vt.

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The idea that many people grow following trauma may be a myth

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Studies of posttraumatic growth are fundamentally flawed and can contribute to toxic cultural narratives, researchers say.

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Kaleigh Young: How gaslighting Manipulates Reality

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Kaleigh Young: How gaslighting Manipulates Reality

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Gaslighting isn’t just between people in a relationship—it involves social power, too

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Kaleigh Young: Vultures prevent tens of millions of metric tons of carbon emissions each year

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Kaleigh Young: Vultures prevent tens of millions of metric tons of carbon emissions each year

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Vultures are hard birds for humans to love. They are an obligate scavenger, meaning they get all their food from already dead prey-and that association has cast them as a harbinger of death since ancient times. But in reality, vultures are nature's flying sanitation crew. And new research adds to that positive picture by detailing these birds' role in a surprising process: mitigating greenhouse gas emissions.

With their impressive vision and the range they can cover in their long, soaring flights, the 22 species of vultures found around the world are often the first scavengers to discover and feed on a carcass. This cleanup provides a vital service to both ecosystems and humans: it keeps nutrients cycling and controls pathogens that could otherwise spread from dead animals to living ones.

Decaying animal bodies release greenhouse gases, including carbon dioxide and methane. But most of these emissions can be prevented if vultures get to the remains first, a new study in Ecosystem Services shows. It calculates that an individual vulture eats between 0.2 and one kilogram (kg) of carcass per day, depending on the vulture species. Left uneaten, each kg of naturally decomposing carcass emits about 0.86 kg of CO2 equivalent. This estimate assumes that carcasses not eaten by vultures are left to decay. But many carcasses are composted or buried by humans, which result in more emissions than natural decay, so vulture consumption can avert even more emissions when replacing those methods. The avoided emissions may not sound like much, but multiply those estimates by the estimated 134 million to 140 million vultures around the world, and the number becomes more impressive: tens of millions of metric tons of emissions avoided per year.

But this ecosystem service is not evenly distributed around the world. It occurs mostly in the Americas, says the study's lead author Pablo Plaza, a biologist at the National University of Comahue in Argentina. Three species found only in the Americas-the Black, Turkey and Yellow-headed vultures-are responsible for 96 percent of all vulture-related emissions mitigation worldwide, Plaza and his colleagues found. Collectively, vultures in the Americas keep about 12 million metric tons of CO2 equivalent out of the atmosphere annually. Using estimates from the U.S. Environmental Protection Agency, that is akin to taking 2.6 million cars off the road each year.

The situation outside of the Americas stands in stark contrast. "The decline in vulture populations in many regions of the world, such as Africa and Asia, has produced a concomitant loss of the ecosystem services vultures produce," Plaza says. The White-rumped Vulture, once one of the most common vultures in India, has been taken to the brink of extinction in just the past few decades. Between 1992 and 2007, its population plummeted by 99.9 percent, from millions of birds to just a few thousand survivors. This steep decline was largely because of poisoning with the veterinary drug diclofenac, to which vultures are exposed when eating dead cattle. In India alone each year, the atmosphere gains at least 2.9 million metric tonsof greenhouse gas emissions that vultures would have prevented before their population crash.

The value of vulture services may be even more important in times of climate disasters or other catastrophes. Carolina Baruzzi, a postdoctoral researcher at the University of Florida, who was not involved in the new study, has documented vulture scavenging after wildlife mass mortality events such as disease outbreaks. "Without vultures," she explains, "we have carcasses decomposing at a slower rate, which can cause a series of problematic issues," including both increased greenhouse gas emissions and disease. Baruzzi's work has shown that the difference between ecosystems with and without vultures isn't a subtle one. If vultures were around, "in two weeks, [carcasses] were usually gone," she says. "Where we didn't have vultures, they stayed there for more than a month and a half or two months-which is really striking."

Vulture conservation is of course not a major climate solution on its own. But according to U.S. Forest Service scientist Grant Domke, that factor and others all add up. "I think the bigger piece here is this idea of a portfolio approach to emissions reduction," says Domke, who leads a team responsible for reporting U.S. forest carbon data as part of the country's commitment to the United Nations Framework Convention on Climate Change. He points to studies on large-scale wildfires that show their detrimental impact on emissions and sequestration has the same order of magnitude as the beneficial effect shown by vultures in the new paper. "Everything needs to be on the table," he says, "and the more we understand about the contributions of plants and animals as part of the economy-wide picture, the better."

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Vultures Prevent Tens of Millions of Metric Tons of Carbon Emissions Each Year

# data[].attributes.attachment_link.description
Vultures are hard birds for humans to love. They are an obligate scavenger, meaning they get all their food from already dead prey-and that association has cast them as a harbinger of death since ancient times. But in reality, vultures are nature's flying sanitation crew.