# data[].attributes.attachment_link.provider_name
The Smithsonian Institution's Human Origins Program

# data[].attributes.attachment_link.readable_text
While the exact number of early human species is debated, on this page are links to summaries of the early human species accepted by most scientists. Click on any species to learn more about it.

Below the summaries is a chart showing the time span during which fossils of each species have been found.

# data[].attributes.attachment_link.description
While the exact number of early human species is debated, on this page are links to summaries of the early human species accepted by most scientists. Click on any species to learn more about it. Below the summaries is a chart showing the time span during which fossils of each species have been found.

# data[].attributes.attachment_link.provider_name
The Smithsonian Institution's Human Origins Program

# data[].attributes.attachment_link.readable_text
New digs and geological dating in Liang Bua Cave, Indonesia, show that Homo floresiensis, nicknamed the "hobbit" for its small size, became extinct around 50,000 years ago - tens of thousands of years earlier than originally thought.

AP Biology Curriculum Materials

Are you an AP Biology teacher? Click here for freely downloadable curriculum materials aligned to the AP learning objectives that use human case studies to teach core evolutionary principles and a resource to help teachers create a comfortable and supportive classroom environment for teaching evolution.

Human Evolution:
Religious Perspectives

The Hall of Human Origins offers a welcoming place to explore one of the most exciting areas of science, the study of human evolution. Despite strong public interest in the science, however, many people find this topic troubling when viewed from a religious perspective. Representatives of diverse religious communities encourage a larger, more respectful understanding of both the scientific evidence and religious belief.

Fun Facts

While other primates are furry, human skin is exposed to the elements. It's not that we're 'naked' - our hair is just really short over much of our bodies. In the warm places where our ancestors lived, evaporation of sweat from exposed skin was a great benefit in cooling our entire bodies. Our brain runs so 'hot', in fact, that sweating and cooling proved vital for evolving our big brain.

# data[].attributes.attachment_link.title
The Smithsonian Institution's Human Origins Program

# data[].attributes.attachment_link.description
New digs and geological dating in Liang Bua Cave, Indonesia, show that Homo floresiensis, nicknamed the "hobbit" for its small size, became extinct around 50,000 years ago - tens of thousands of years earlier than originally thought. Are you an AP Biology teacher?

# data[].attributes.body
read the lesson carefully, before answering the pronote quizz

# data[].attributes.attachment_link.readable_text
Reading trees: A quick review

What's the difference between a phylogeny, an evolutionary tree, a phylogenetic tree, and a cladogram?

For general purposes, not much. This site, along with many biologists, use these terms interchangeably — all of them essentially mean a tree structure that represents the evolutionary relationships within a group of organisms. The context in which the term is used will tell you more details about the representation (e.g., whether the tree's branch lengths represent nothing at all, genetic differences, or time; whether the phylogeny represents a reconstructed hypothesis about the history or the organisms or an actual record of that history; etc.) However, some biologists do use these words in more specific ways. To some biologists, use of the term "cladogram" emphasizes that the diagram represents a hypothesis about the actual evolutionary history of a group, while "phylogenies" represent true evolutionary history. To other biologists, "cladogram" suggests that the lengths of the branches in the diagram are arbitrary, while in a "phylogeny," the branch lengths indicate the amount of character change. The words "phylogram" and "dendrogram" are also sometimes used to mean the same sort of thing with slight variations. These vocabulary differences are subtle and are not consistently used within the biological community. For our purposes here, the important things to remember are that organisms are related and that we can represent those relationships (and our hypotheses about them) with tree structures.

# data[].attributes.attachment_link.description
Reading trees: A quick review What's the difference between a phylogeny, an evolutionary tree, a phylogenetic tree, and a cladogram? For general purposes, not much.

# data[].attributes.body
Write a text explaining the difference you notice between Carl Linnaeus system of classification and phylogenetic classification

# data[].attributes.attachment_link.readable_text
Using trees for classification

Clearly, evolutionary trees convey a lot of information about a group's evolutionary history. Biologists are taking advantage of this by using a system of phylogenetic classification, which conveys the same sort of information that is conveyed by trees. In contrast to the traditional Linnaean system of classification, phylogenetic classification names only clades. For example, a strictly Linnaean system of classification might place the birds and the non-Avian dinosaurs into two separate groups. However, the phylogeny of these organisms reveals that the bird lineage actually branches off of the dinosaur lineage, and so, in phylogenetic classification, the birds should be considered a part of the group Dinosauria.

Advantages of phylogenetic classification
Phylogenetic classification has two main advantages over the Linnaean system. First, phylogenetic classification tells you something important about the organism: its evolutionary history. Second, phylogenetic classification does not attempt to "rank" organisms. Linnaean classification "ranks" groups of organisms artificially into kingdoms, phyla, orders, etc. This can be misleading as it seems to suggest that different groupings with the same rank are equivalent. For example, the cats (Felidae) and the orchids (Orchidaceae) are both family level groups in Linnaean classification. However, the two groups are not comparable:

One has a longer history than the other. The first representatives of the cat family Felidae probably lived about 30 million years ago, while the first orchids may have lived more than 100 million years ago.

The have different levels of diversity. There are about 35 cat species and 20,000 orchid species.

They have different degrees of biological differentiation. Many orchids belonging to different genera are able to hybridize. But the same is not true of cats — house cats (belonging to the genus Felis) and lions (belonging to the genus Panthera) cannot form hybrids.

There is just no reason to think that any two identically ranked groups are comparable and by suggesting that they are, the Linnaean system is misleading. So it seems that there are many good reasons to switch to phylogenetic classification. However, organisms have been named using the Linnaean system for many hundreds of years. How are biologists making the transition to phylogenetic classification?

Switching to phylogenetic classification

Biologists deal with phylogenetic classification by de-emphasizing ranks and by reassigning names so that they are only applied to clades. This means that your use of biological names doesn't have to change very much. In many cases, the Linnaean names are perfectly good in the phylogenetic system. For example, Aves, which is the class of birds in the Linnaean system, is also used as a phylogenetic name, since birds form a clade (right).
Most of the specific names that you are accustomed to using (e.g., Homo sapiens, Drosophila melanogaster) have not changed at all with the rise of phylogenetic classification. However, there are some names from Linnaean classification that do NOT work in a phylogenetic classification. For example, the reptiles do not form a clade (and cannot be a named group in the phylogenetic system) — unless you count birds as members of Reptilia too.

# data[].attributes.attachment_link.description
Using trees for classification Clearly, evolutionary trees convey a lot of information about a group's evolutionary history. Biologists are taking advantage of this by using a system of phylogenetic classification, which conveys the same sort of information that is conveyed by trees. In contrast to the traditional Linnaean system of classification, phylogenetic classification names only clades.

# data[].attributes.attachment_link.readable_text
Phylogenetic systematics, a.k.a. evolutionary trees :

Reconstructing trees: Cladistics

Cladistics is a method of hypothesizing relationships among organisms — in other words, a method of reconstructing evolutionary trees. The basis of a cladistic analysis is data on the characters, or traits, of the organisms in which we are interested. These characters could be anatomical and physiological characteristics, behaviors, or genetic sequences.

The result of a cladistic analysis is a tree, which represents a supported hypothesis about the relationships among the organisms. However, it is important to keep in mind that the trees that come out of cladistic analyses are only as good as the data that go into them. New and better data could change the outcome of a cladistic analysis, supporting a different hypothesis about the way that the organisms are related.

Assumptions
There are three basic assumptions in cladistics:

1. Change in characteristics occurs in lineages over time.
The assumption that characteristics of organisms change over time is the most important one in cladistics. It is only when characteristics change that we are able to recognize different lineages or groups. We call the "original" state of the characteristicplesiomorphic and the "changed" state apomorphic.

# data[].attributes.attachment_link.description
Phylogenetic systematics, a.k.a. evolutionary trees : Reconstructing trees: Cladistics Cladistics is a method of hypothesizing relationships among organisms - in other words, a method of reconstructing evolutionary trees. The basis of a cladistic analysis is data on the characters, or traits, of the organisms in which we are interested.

# data[].attributes.body
Watch carefully the video 1 and answer the quizz

# data[].attributes.body
how to build an evolutionary tree

# data[].attributes.attachment_link.readable_text
Phylogenetic systematics, a.k.a. evolutionary trees :

Reconstructing trees: A simple example

Now we'll go through a simple example based on the steps just described.

1. Choose the taxa. You decide to study the major clades of vertebrates shown in the leftmost column of the table below. (Note that many vertebrate lineages are excluded from this example for the sake of simplicity.)

2. Determine the characters. After studying the vertebrates, you select a set of traits, which seem to be homologies, and build the following data table to record your observations. (Note that many relevant vertebrate characters are excluded from this example for the sake of simplicity.)

3. Determine the polarity of characters. From studying fossils and outgroups closely related to the vertebrate clade, you hypothesize that the ancestor of vertebrates had none of these features.

4. Group taxa by synapomorphies. Since we have a good idea of what the ancestral characters are (see above), this is not so hard. We might start out by examining the egg character. We focus in on the group of lineages that share the synapomorphic form of this character, an amniotic egg (A, below), and hypothesize that they form a clade (B):

We go through the whole table like this, grouping clades according to synapomorphies (C):

5. Work out conflicts that arise. There are no conflicts here. Every group is a subset of another group (see C above).

6. Build your tree. Based on the groupings above, you produce this tree:

7. Voila! You have made a phylogeny.

Of course, this was just an example of the tree-building process. Phylogenetic trees are generally based on many more characters and often involve more lineages. For example, biologists reconstructing relationships between 499 lineages of seed plants began with more than 1400 molecular characters!

# data[].attributes.attachment_link.description
Phylogenetic systematics, a.k.a. evolutionary trees : Reconstructing trees: A simple example Now we'll go through a simple example based on the steps just described. Choose the taxa. You decide to study the major clades of vertebrates shown in the leftmost column of the table below.

# data[].attributes.attachment_link.readable_text
Human evolution

Evolutionary biologists are interested in understanding how humans fit into the history of life and how the processes of evolution have shaped us. Much scientific effort goes into studying human evolution, and as a result, our understanding of this area is moving forward rapidly, as new evidence emerges and hypotheses are tested, confirmed, discarded, or modified.

The location of our very own twig: Humans on the tree of life
This tree is based on morphological and genetic data. Chimpanzees and humans form a clade with DNA sequences that differ by only 1%. This genetic similarity made it hard to figure out exactly how these two primates are related, but recent genetic studies have strongly suggested that chimpanzees and humans are each other's closest living relative.

# data[].attributes.attachment_link.description
Human evolution Evolutionary biologists are interested in understanding how humans fit into the history of life and how the processes of evolution have shaped us. Much scientific effort goes into studying human evolution, and as a result, our understanding of this area is moving forward rapidly, as new evidence emerges and hypotheses are tested, confirmed, discarded, or modified.

# data[].attributes.headline
Draft genome sequence of the common chimpanzee

# data[].attributes.subject
Draft genome sequence of the common chimpanzee

# data[].attributes.attachment_link.readable_text
Human evolution (2 of 2)

How did humans evolve?
About six million years ago in Africa, the chimpanzee lineage and our own split. What happened to us after that split? The hominid lineage did not march in a straight line to Homo sapiens. Instead, the early hominid lineage gave rise to many other (now extinct) hominids. Examining the fossils, the artifacts, and even the DNA of these relatives has helped us understand how this complex hominid tree evolved, and how modern humans came to exist.

Here are some of the important events in human history, with approximate dates, which reflect the evidence currently available:

2) Before 4 mya: The hominid Australopithecus anamensis walked around what is now Kenya on its hind legs.

3) 3 mya: Australopithecus afarensis (" Lucy") lived in Africa.

4) 2.5 mya: Some hominids made tools by chipping stones to form a cutting edge. There were perhaps four or more species of hominid living in Africa.

5) 2 mya: The first members of the Homo clade, with their relatively large brains, lived in Africa.

6) 1.5 mya: Hand axes were used. Also, hominids had spread out of Africa and into much of Asia and Europe. These hominids included the ancestors of Neanderthals ( Homo neanderthalensis) in Europe and Homo erectus in Asia.

7) 100,000 years ago: Human brains reached more or less the current range of sizes. Early Homo sapiens lived in Africa. At the same time, Homo neanderthalensis and Homo erectus lived in other parts of the Old World.

8) 50,000 years ago: Human cultures produced cave paintings and body adornment, and constructed elaborate burials. Also, some groups of modern humans extended their range beyond Africa.

9) 25,000 years ago: Other Homo species had gone extinct, leaving only modern humans, Homo sapiens, spread throughout the Old World.

# data[].attributes.attachment_link.description
Human evolution (2 of 2) How did humans evolve? About six million years ago in Africa, the chimpanzee lineage and our own split. What happened to us after that split? The hominid lineage did not march in a straight line to Homo sapiens. Instead, the early hominid lineage gave rise to many other (now extinct) hominids.

# data[].attributes.attachment_link.readable_text
Trees, not ladders

Several times in the past, biologists have committed themselves to the erroneous idea that life can be organized on a ladder of lower to higher organisms. This idea lies at the heart of Aristotle's Great Chain of Being (see right).

Similarly, it's easy to misinterpret phylogenies as implying that some organisms are more "advanced" than others; however, phylogenies don't imply this at all.

In this highly simplified phylogeny, a speciation event occurred resulting in two lineages. One led to the mosses of today; the other led to the fern, pine, and rose. Since that speciation event, both lineages have had an equal amount of time to evolve. So, although mosses branch off early on the tree of life and share many features with the ancestor of all land plants, living moss species are not ancestral to other land plants. Nor are they more primitive. Mosses are the cousins of other land plants.

So when reading a phylogeny, it is important to keep three things in mind:

Evolution produces a pattern of relationships among lineages that is tree-like, not ladder-like.

Just because we tend to read phylogenies from left to right, there is no correlation with level of "advancement."

For any speciation event on a phylogeny, the choice of which lineage goes to the right and which goes to the left is arbitrary. The following phylogenies are equivalent:

Biologists often put the clade they are most interested in (whether that is bats, bedbugs, or bacteria) on the right side of the phylogeny.

Misconceptions about humans
The points described above cause the most problems when it comes to human evolution. The phylogeny of living species most closely related to us looks like this:

It is important to remember that:

1. Humans did not evolve from chimpanzees. Humans and chimpanzees are evolutionary cousins and share a recent common ancestor that was neither chimpanzee nor human.

2. Humans are not "higher" or "more evolved" than other living lineages. Since our lineages split, humans and chimpanzees have each evolved traits unique to their own lineages.

# data[].attributes.attachment_link.description
Trees, not ladders Several times in the past, biologists have committed themselves to the erroneous idea that life can be organized on a ladder of lower to higher organisms. This idea lies at the heart of Aristotle's Great Chain of Being (see right).

# data[].attributes.attachment_link.readable_text
Resource library : Evo in the news :
Got lactase?
April 2007

In the US and many other countries, we've certainly "got milk," but not everyone can enjoy it. For around 10% of Americans, 10% of Africa's Tutsi tribe, 50% of Spanish and French people, and 99% of Chinese, a tall cold glass of milk means an upset stomach and other unpleasant digestive side effects. In fact, most adults in the world are lactose intolerant and cannot digest lactose, the primary sugar in milk. And yet, regardless of our ancestry, most of us began our lives happily drinking milk from a bottle or breast — so what happened in the intervening time? Why do so many babies enjoy lactose and so many adults avoid it? Lactose is broken down by a protein called lactase, which acts as a pair of molecular scissors, snipping the lactose molecule in two. Anyone who drank milk as a baby carries a working version of the gene that codes for lactase. In lactose tolerant individuals, that gene keeps working into adulthood, producing the protein that digests lactose and makes eating ice cream a pleasant experience. But in people who are lactose intolerant, that lactase gene is switched off after weaning. Now, new research reveals that the Stone Age ancestors of European dairy-lovers probably couldn't digest milk either. So how did they get from bellyaches to milk mustaches? The answer is an evolutionary story that takes us from the milkmaids of the Alps to the Maasai herdsmen of Africa.
Where's the evolution?
Mutations that keep the lactase gene permanently switched on are common among modern Europeans — but not among their ancestors. In March 2007, a team of German and British researchers announced that they went looking for that mutation in the 7000-year-old fossils of ancient Europeans and came up empty-handed. The researchers managed to extract the length of DNA corresponding to the lactose tolerance mutation from eight Neolithic human fossils and one Mesolithic fossil, but those DNA sequences did not carry the telltale mutation. The results suggest that as late as 5000 BC most ancient Europeans could not have digested milk as adults — and that they only later evolved into milk-drinking societies.
Today, the ability to digest milk as an adult seems like a clear benefit, but that wasn't always the case. Lactose tolerance is only advantageous in environments and cultures where humans have access to domesticated dairy animals. Multiple lines of evidence from human genetics, cattle genetics, and archaeological records suggest that Middle Eastern and North Africans populations domesticated cattle between 7500 and 9000 years ago, and that these animals were later brought into Europe. In that cow-friendly environment, being able to drink milk directly (instead of having to process it into lower-lactose cheese) would have been advantageous, providing additional sustenance and, during droughts, a source of water. The lactose tolerance mutation arose randomly (as all mutations do), but once it arose, it had a distinct advantage in these populations. Natural selection would have favored individuals carrying the lactose tolerance mutation, spreading it through ancient European populations that depended on dairying. Many thousands of years later, we see the indirect (but delicious) effects of this mutation's success in European cuisines: oozing French cheeses, Swiss milk chocolate, and creamy Italian gelatos.

How do we know?
How did Sarah Tishkoff's team identify the African lactose tolerance mutations and show that they had been advantageous? To identify the mutations, the team collected DNA samples from African participants and tested those same individuals for lactose tolerance. They looked for mutations in the DNA samples that always showed up in lactose tolerant individuals but weren't found in lactose intolerant individuals. To double check that the candidate mutations they'd identified weren't red herrings, the team then did Petri-dish-style experiments, which helped show that those signature mutations were likely to keep the lactase gene turned on.

Surprisingly, with respect to dairying, human populations on separate continents seem to have led parallel lives — or rather, followed parallel evolutionary trajectories. Recent evidence suggests that cattle may have been domesticated independently in several places, including Africa. As African populations began herding cattle, lactose tolerance became an advantageous trait. The stage was set, in Africa too, for the spread of a lactose tolerance mutation. In January 2007, an international team of researchers led by geneticist Sarah Tishkoff announced that they had uncovered the genetic roots of Africans' lactose tolerance. Just as in Europe, on this continent, mutations (in this case, probably three) randomly arose, and these happened to have the effect of keeping the lactase gene switched on. And just as in Europe, these mutations were favored by natural selection and quickly spread through dairy-dependent populations.
While this discovery answers many questions, it also highlights new mysteries. For example, Tishkoff's team discovered that in the Hadza population (a group of Tanzanian hunter-gatherers), around 50% are lactose tolerant — a percentage usually indicative of a dairy-dependent society. And yet, as far as is known, the Hadza have never had much to do with cattle or relied on milk in their diets — so what explains their lactose tolerance? Are they the long lost descendents of a group of cattle herders? Has the tribe changed its basic mode of making a living? Or could the lactose tolerance mutation provide some other yet-to-be-discovered advantage, beyond allowing adults to drink milk?

Whatever the answers such spin-off questions, research into the evolutionary origins of lactose tolerance has already clearly illuminated some fascinating aspects of human evolutionary history. Perhaps most intriguingly, the convergent evolution of African and European populations in relation to cattle domestication reveals that shared aspects of human culture across different ethnic groups affects our evolution in similar ways. Regardless of skin color or geography — whether dealing with Stone Age Europeans, Swiss milk maids, Maasai warriors, or modern hunter-gatherers — evolution plays by the same rules.

Read more about it

Primary literature:

Burger, J., Kirchner, M., Bramanti, B., Haak, W., and Thomas, M. G. (2007). Absence of the lactase-persistence-associated allele in early Neolithic Europeans. Proceedings of the National Academy of Sciences USA 104(10):3736-3741.

Check, E. (2007). How Africa learned to love the cow. Nature 444:994-996.

Tishkoff, S. A., Reed, F. A., Ranciaro, A., Voight, B. F., Babbitt, C. C., Silverman, J. S., Powell, K., Mortensen, H. M., Hirbo, J. B., Osman, M., Ibrahim, M., Omar, S. A., Lema, G., Nyambo, T. B., Ghori, J., Bumpstead, S., Pritchard, J. K., Wray, G. A., and Deloukas, P. (2007). Convergent adaptation of human lactase persistence in Africa and Europe. Nature Genetics 39:31-40.

News articles:

Understanding Evolution resources:

Discussion and extension questions

1. Are you lactose tolerant or lactose intolerant? Based on the information in this article, explain how your genes affect your ability (or lack of ability) to digest milk.

2. Read about the concepts of genotype and phenotype. Explain how these concepts apply to a lactose tolerant individual.

3. Review some background information on natural selection. Explain how a lactose tolerance mutation would spread through a human population that herds cattle. Make sure to include the concepts of variation, selection, and inheritance in your explanation.

4. Now imagine that the population described in the question above lived during the Paleolithic before any animals were domesticated. How would that change your answer to the question above?

5. In evolutionary terms, why is it surprising that many Hadza are lactose tolerant?

6. This article describes an example of convergent evolution in humans. Research a different example of convergent evolution in another organism. Explain, in general terms, how that trait evolved in the different organisms.

Related lessons and teaching resources

Teach about natural selection: This board game for grades 9-12 simulates natural selection. It is suitable for an introductory biology class and for more advanced classes where you could go into more detail on important principles such as the role of variation and mutation.

Teach about human evolution at a molecular level: In this lesson for grades 9-12, students investigate variation in the beta globin gene by identifying base changes that do and do not alter function, and by using several internet-based resources to consider the significance in different environments of the base change associated with sickle cell disease.

References

Burger, J., Kirchner, M., Bramanti, B., Haak, W., and Thomas, M. G. (2007). Absence of the lactase-persistence-associated allele in early Neolithic Europeans. Proceedings of the National Academy of Sciences USA 104(10):3736-3741.

Central Intelligence Agency. (2007, March 15). The world factbook: United States.
Retrieved March 27, 2007 fromhttps://www.cia.gov/cia/publications/factbook/print/us.html

Check, E. (2007). How Africa learned to love the cow. Nature 444:994-996.

National Digestive Diseases Information Clearinghouse. (2006, March). Lactose intolerance.
Retrieved March 27, 2007 fromhttp://digestive.niddk.nih.gov/ddiseases/pubs/lactoseintolerance/

Tishkoff, S. A., Reed, F. A., Ranciaro, A., Voight, B. F., Babbitt, C. C., Silverman, J. S., Powell, K., Mortensen, H. M., Hirbo, J. B., Osman, M., Ibrahim, M., Omar, S. A., Lema, G., Nyambo, T. B., Ghori, J., Bumpstead, S., Pritchard, J. K., Wray, G. A., and Deloukas, P. (2007). Convergent adaptation of human lactase persistence in Africa and Europe. Nature Genetics 39:31-40.

Wade, N. (2007, December 11). Lactose tolerance in East Africa points to recent evolution. The New York Times.
Retrieved March 27, 2007 fromhttp://www.nytimes.com/2006/12/11/science/11evolve.html?ex=1323493200&
en=a2ded9bbd0241eaf&ei=5088&partner=rssnyt&emc=rss

# data[].attributes.attachment_link.description
Resource library : Evo in the news : Got lactase? April 2007 In the US and many other countries, we've certainly "got milk," but not everyone can enjoy it. For around 10% of Americans, 10% of Africa's Tutsi tribe, 50% of Spanish and French people, and 99% of Chinese, a tall cold glass of milk means an upset stomach and other unpleasant digestive side effects.

# data[].attributes.attachment_link.provider_name
Understanding Evolution - Your one-stop source for information on evolution

# data[].attributes.attachment_link.readable_text
The narratives of human evolution are oft-told and highly contentious. There are major disagreements in the field about whether human evolution is more like a branching tree or a crooked stick, depending partly on how many species one recognizes. Interpretations of almost every new find will be sure to find opposition among other experts. Disputes often center on diet and habitat, and whether a given animal could walk bipedally or was fully upright. What can we really tell about human evolution from our current understanding of the phylogenetic relations of hominids and the sequence of evolution of their traits?

To begin with, let's take a step back. Although the evolution of hominid features is sometimes put in the framework of "apes vs. humans," the fact is that humans are apes, just as they are primates and mammals. A glance at the evogram shows why. The other apes - chimp, bonobo, gorilla, orangutan, gibbon - would not form a natural, monophyletic group (i.e., a group that includes all the descendants of a common ancestor) - if humans were excluded. Humans share many traits with other apes, and those other "apes" (i.e., non-human apes) don't have unique features that set them apart from humans. Humans have some features that are uniquely our own, but so do gorillas, chimps, and the rest. Hominid evolution should not be read as a march to human-ness (even if it often appears that way from narratives of human evolution). Students should be aware that there is not a dichotomy between humans and apes. Humans are a kind of ape.

Virtually all systematists and taxonomists agree that we should only give names to monophyletic groups. However, this evogram shows that this guideline is not always followed. For an example, consider Australopithecus. On the evogram you can see a series of forms, from just after Ardipithecus to just before Homo in the branching order, that are all called Australopithecus. (Even Paranthropus is often considered an australopithecine.) But as these taxa appear on the evogram, "Australopithecus" is not a natural group, because it is not monophyletic: some forms, such as A. africanus, are found to be closer to humans than A. afarensis and others. Beyond afarensis, for example, all other Australopithecus and Homo share "enlarged cheek teeth and jaws," because they have a more recent common ancestor. Eventually, several of these forms will have to have new genus names if we want to name only monophyletic groups. Students should avoid thinking of "australopithecines" as a natural group with uniquely evolved traits that link its members together and set it apart from Homo. Instead they should focus on the pattern of shared traits among these species and the Homo clade, recognizing that each species in this lineage gains more and more features that are shared by Homo.

In popular fiction and movies, the concept of the wild "ape-man" is often that of a tree-living, vine-swinging throwback like Tarzan. However, the pantheon of hominids is much richer than this, as the evogram shows with forms as different as Paranthropus and Ardipithecus shows. For example, imagine going back in time to the common ancestor of humans and chimps (including bonobos). What did that common ancestor look like? In the Origin of Species Darwin noted that the extinct common ancestor of two living forms should not be expected to look like a perfect intermediate between them. Rather, it could look more like one branch or the other branch, or something else entirely.

Did the common ancestor of humans and chimps conform to the ape-man myth and live in the trees, swinging from vines? To answer this, we have to focus not only on anatomy but on behavior, and we have to do it in a phylogenetic context. Apes such as the gibbon and orangutan, which are more distantly related to humans, are largely arboreal (i.e., tree-living). The more closely related apes such as the gorilla and chimps are relatively terrestrial, although they can still climb trees. The feet of the first hominids have a considerable opposition of the big toe to the others but relatively flat feet, as arboreal apes generally do. But other features of their skeleton, such as the position of the foramen magnum underneath the skull, the vertically shortened and laterally flaring hips, and the larger head of the femur, suggest that they were not just mainly terrestrial but habitually bipedal, unlike their knuckle-walking relatives. Most evidence suggests that the hominid lineage retained some of the anatomical features related to arboreal life and quadrupedal gait even after it had evolved a more terrestrial lifestyle and a bipedal gait. There is no fossil record of these behaviors, but the balance of the available evidence supports the hypothesis that the hominid ancestor was terrestrial and bipedal.

Much discussion in human paleontology surrounds the evolution of a bipedal, upright stance. When and why did this occur? One thing to keep in mind is that "bipedal" and "upright" are not equivalent terms. An animal can be bipedal without having a vertical backbone (think T. rex). It seems clear from the fossil record of hominids that habitual bipedality preceded the evolution of a recurved spine and upright stance. Other changes in the gait, such as how the relatively "splayed" gait of chimps evolved into the gait of humans, who put one foot directly in front of the other, involve studying the hip joint, the femur, and the foot. The famous Laetoli footprints attributed to Australopithecus afarensis are bipedal, but they are still relatively splayed compared to the tracks of living humans.

Another extremely interesting feature in hominid evolution is the degree of sexual dimorphism (i.e., physical differences between the sexes) in different species. Sexual dimorphism is linked to features of sociality and mate competition in many sorts of animals. To understand the evolution of this feature in humans, which have relatively low sexual dimorphism, we need to consider the other apes, in which sexual dimorphism tends to be moderate to high (with exceptions). We don't have sufficient evidence about Sahelanthropus, Orrorin, and Ardipithecus to understand much about sex differences in these species, but we do know that A. afarensis had relatively high sexual dimorphism: the males were considerably larger than the females. The difference seems to have been less in A. africanus, Paranthropus, and most of the Homo lineage. The evolutionary explanation for A. afarensis' dimorphism is not entirely clear. The larger males may have used their size to attract females and/or repel rivals, which would fit with an explanation based on sexual selection. Or the males and females may have been differently sized because they played different roles in their groups, the males hunting and gathering and the females caring for the young. Darwin thought that this differentiation of the sexes may have played a critical role in human evolution, but we simply do not know much about the role of this feature in A. afarensis. Some, all, or none of these functions may have been in play.

We do know that by the time the animals known as Homo evolved, they could make tools, and their hands were well suited for complex manipulations. These features were eventually accompanied by the reduction of the lower face, particularly the jaws and teeth, the recession of the brow, the enlargement of the brain, the evolution of a more erect posture, and the evolution of a limb more adapted for extended walking and running (along with the loss of arboreally oriented features). The evogram shows the hypothesized order of acquisition of these traits. Yet each of the Homo species was unique in its own way, so human evolution should not be seen as a simple linear progression of improvement toward our own present-day form.

# data[].attributes.attachment_link.title
The emergence of humans - Understanding Evolution

# data[].attributes.attachment_link.description
The narratives of human evolution are oft-told and highly contentious. There are major disagreements in the field about whether human evolution is more like a branching tree or a crooked stick, depending partly on how many species one recognizes. Interpretations of almost every new find will be sure to find opposition among other experts.

# data[].attributes.attachment_link.readable_text
Fossil Hominids, Human Evolution: Thomas Huxley & Eugene Dubois
When Charles Darwin wrote the Origin of Species, he had to wonder about how humans came to be. Humans had hereditary variation in every generation, and some individuals had more children than others — the key ingredients for natural selection. But he chose not to write about humans in his first book about evolution, in large part out of strategy. In 1857, two years before Darwin published the Origin of Species, Wallace asked him in a letter if he would discuss the origin of mankind in the book. Darwin replied, "I think I shall avoid the whole subject, as so surrounded with prejudices, though I fully admit that it is the highest and most interesting problem for the naturalist."
But Darwin also knew that he had no fossil record to use to develop a hypothesis about human evolution. Over the years, naturalists had uncovered a few stone tools lying alongside the fossils of extinct mammals. But even in the 1800s, these relics were considered to be only a few thousand years old, and to have been made by lost tribes of savages.

First human fossils discovered
Even when the first part of a fossil human came to light in 1857, naturalists had a hard time recognizing it for what it truly was. German miners working at the Feldhofer Grotto in the Neander valley dug up a skullcap. It looked somewhat human, but it was remarkably thick and sported a massive brow ridge. Did it belong to an ancient individual from a human-like species now extinct? Or was Neanderthal man just an extreme member of Homo sapiens? One of the German naturalists who described the skull for the first time, Herman Schaaffhausen, was convinced of the latter. He ignored evidence that the skull had been found alongside extinct cave bears and mammoths, and claimed that it was some recent barbarian, perhaps a member of one of the wild tribes mentioned by Roman historians.

Shortly after Darwin published the Origin of Species, his great champion Thomas Huxley (right) considered the skull from the Neander valley. Huxley shared some of the Euro-centric notions of his time. Based on their skulls, it was thought that Europeans had the best-developed brains, compared to the Australian aborigines with skulls having relatively low profiles and thicker brows. This view led Huxley to consider Neanderthals as occupying a slightly lower position within Homo sapiens.

Darwin publishes on human origins
Amid these ambiguous developments, Darwin decided to say something about human origins. In 1871 he published The Descent of Man and Selection in Relation to Sex, in which he argued that all of the known evidence was consistent with humans having evolved from a common ancestor shared with apes. He speculated that Africa was their place of origin and that human ancestors had gradually taken on their current form since then. He suggested that natural selection was not the only evolutionary pressure at work. Women might have preferred different traits in men, what Darwin called sexual selection, and this might have given rise to differences between the races. Darwin's ideas did not persuade his old correspondent, Alfred Russel Wallace. Wallace decided that our oversized brains were far more powerful than necessary — we could easily survive with minds slightly more advanced than an ape's. The creation of humans must, he concluded, be the work of divine intervention.

More human fossils discovered
Fossils would be crucial to resolving this debate, but they were slow in coming. It was not until 1886 that Neanderthal fossils were discovered for a second time — and this time, they included the jaw and other parts of the skeleton. Found in Spy, Belgium, these clearly came from ancient rocks, demonstrating that Neanderthals were not some barbarian tribe that lived a few centuries ago. The next year, Eugene Dubois (left), a young anatomist from Holland traveled to Indonesia in the hopes of finding fossils of early man. Since orangutans lived there, and since Dubois managed to secure a job as a medical officer in the Royal Dutch East Indies Army, it seemed like a good place for him to go prospecting. After four years of struggles, he hit pay dirt when he dug a pit in the side of the Solo River in eastern Java. He found fossil remains of something not quite human, but not quite ape. It stood upright, but its brain was far too small to qualify as human. It became known as Pithecanthropus erectus, meaning "upright ape-man."

Fossil evidence and the acceptance of human evolution
Dubois came back to Europe in 1895 to champion his discovery. He met with some stiff opposition from skeptics. Some wondered whether the ape-like skull and the human-like femur came from the same skeleton. Others thought the skull was similar to Neanderthals. Dubois became embittered by the debate over his bones and hid the fossils from other scientists. But in time, as more fossils were uncovered in Asia, scientists came to recognize that Dubois had indeed found the first representative of the ancient species, Homo erectus.
The twentieth century brought a great many more fossils of humans and hominids. Today twenty hominid species have been identified, the oldest of which date back six million years. They point to an African origin, as Darwin had proposed. Hominid evolution was sometimes pictured as a single line of descent and a steady progression from primitive forms to more advanced forms. The fossils suggested otherwise. Instead, hominid evolution produced a dense thicket of branches, with several species co-existing at any given time except for the last 30,000 years or so. Added to this wealth of data is the knowledge gathered from comparisons of DNA from humans, apes, and even Neanderthals. While many questions remain to be answered about human evolution, scientists have a growing treasury of evidence at their disposal.

# data[].attributes.attachment_link.title
Fossil Hominids, Human Evolution: Thomas Huxley & Eugene Dubois

# data[].attributes.attachment_link.description
Fossil Hominids, Human Evolution: Thomas Huxley & Eugene Dubois When Charles Darwin wrote the Origin of Species, he had to wonder about how humans came to be. Humans had hereditary variation in every generation, and some individuals had more children than others - the key ingredients for natural selection.

# data[].attributes.attachment_link.provider_name
The Smithsonian Institution's Human Origins Program

# data[].attributes.attachment_link.description
Smithsonian National Museum of Natural History

# data[].attributes.attachment_link.provider_name
The Smithsonian Institution's Human Origins Program

# data[].attributes.attachment_link.description
Smithsonian National Museum of Natural History

# data[].attributes.body
Watch carefully the video and answer the "quizz activity 1"

# data[].attributes.attachment_link.title
Human Evolution: We Didn't Evolve From Chimps: Crash Course Biology #19

# data[].attributes.attachment_link.readable_text
La découverte d' Homo naledi, dernière branche en date de notre arbre généalogique, ravive le débat sur l'évolution humaine, et impose un rappel des bases que nous avons tous oubliées. Voici les réponses à quelques questions courantes.
Pourquoi les scientifiques sont-ils certains que l'évolution humaine a bien eu lieu ?
Il y a plusieurs raisons. Nous partageons près de 99 % de notre séquence génétique avec les chimpanzés et les bonobos, ce qui suggère fortement que nous avons un ancêtre commun. De plus, des milliers de fossiles indiquent l'existence d'espèces marquant une progression vers l'être humain dans l'évolution de notre lignée après sa séparation d'avec les autres grands singes puis, plus tard, d'avec les chimpanzés et les bonobos.

Les biologistes ont observé d'autres espèces évoluer, à la fois sur le terrain et en laboratoire. L'émergence de microbes résistants aux antibiotiques est une forme d'évolution. De plus, les éleveurs pratiquent l'évolution en permanence : il suffit de réfléchir à l'incroyable diversité des races de chiens créées à partir des loups.
L'évolution contredit-elle la Bible ?
Oui, si vous croyez en une interprétation littéraire de la Bible. Elle contredit l'histoire de la Genèse selon laquelle Dieu a créé tous les organismes sous leur forme actuelle. Mais il est possible de croire en Dieu sans croire littéralement à tout ce qui est dit dans la Bible.
Mais alors, comment est-ce que ça marche, l'évolution ?
L'ADN qui compose nos gènes et ceux de tous les organismes sur Terre, à l'exception de quelques virus, peut subir des mutations aléatoires. De temps en temps, ces mutations peuvent toucher une caractéristique importante, telle que la couleur de la robe d'un animal ou un comportement particulier. Les éleveurs sélectionnent les animaux à reproduire en fonction des caractéristiques qu'ils recherchent. C'est ce qu'on appelle la sélection artificielle. Dans la nature, la sélection est faite par l'environnement de l'animal ainsi que par le sexe opposé.

Par exemple, si un animal naît avec une robe d'une couleur qui le protège mieux des prédateurs, il pourra survivre plus longtemps et enfanter plus de progénitures. Si les partenaires sexuels sont plus sensibles à un individu qui fait la cour plus longtemps, ce dernier aura plus de succès reproductifs. Sur la durée, les mutations favorables se propagent dans la population et changent son apparence. Sur une durée suffisante, le processus peut même engendrer de nouvelles espèces.
Quelles sont les plus grandes étapes de l'évolution humaine ?
La lignée humaine s'est séparée de celle des grands singes il y a au moins sept millions d'années et au plus 13 millions d'années. Les membres incontestés les plus récents de notre lignée à avoir marché debout régulièrement sont les australopithèques, dont l'espèce la plus célèbre est celle de Lucy, l' Australopithecus afarensis. (Lucy remonte quant à elle à 3,2 millions d'années.) Le fossile connu le plus ancien attribué à notre genre, Homo, remonte à environ 2,8 millions d'années et n'a été découvert que cette année. On pensait autrefois que la capacité à fabriquer des outils de pierre était la caractéristique principale de notre genre. Mais on estime que les plus anciens outils retrouvés à ce jour datent en fait d'il y a 3,3 millions d'années. Soit ils ont été fabriqués par des australopithèques tels que Lucy, soit les scientifiques n'ont tout simplement pas encore retrouvé les formes primitives d' Homo qui les ont fabriqués. A l'instar des australopithèques, les premières espèces d' Homo telles qu' Homo erectus et Homo habilis marchaient sur deux jambes.

Il y a un débat incessant sur l'époque à laquelle nos ancêtres ont commencé à dompter le feu, il y a entre 1,8 millions d'années et 800 000 ans. Une théorie affirme que l'invention de la cuisson nous a permis de récupérer plus d'énergie dans la viande, ce qui aurait alimenté l'évolution spectaculaire du cerveau humain. L'augmentation de la taille du cerveau et la dextérité des mains ont l'une après l'autre contribué aux développements de caractéristiques typiques des humains, comme le langage complexe, l'art et l'agriculture. Ces trois caractéristiques sont apparues au cours des 100 000 dernières années.
Où est-ce que cela s'est produit, et pourquoi est-il utile de le savoir ?
Il existe la preuve génétique et fossile que jusqu'à récemment, l'évolution humaine a eu lieu en Afrique. Ce qu'on ne sait pas en revanche, c'est si les premiers Homo sont apparus dans le sud ou dans l'est de l'Afrique. Il est important de savoir où notre espèce a évolué, car c'est cet environnement qui a façonné la composition génétique qui est encore la nôtre aujourd'hui. Notre lieu d'origine est le premier chapitre d'une longue histoire qui mène jusqu'à aujourd'hui.

Il y a environ 60 000 ans, d'après les preuves génétiques et fossiles, les humains modernes ont quitté l'Afrique pour coloniser le monde. Des éléments génétiques suggèrent que peu de temps après ce départ, les humains modernes se sont parfois reproduits avec les Néandertaliens et une mystérieuse population asiatique appelée les Dénisoviens. Homo Sapiens est désormais la seule espèce humaine sur Terre. Mais ce n'est le cas que depuis 30 000 ans.
Pourquoi les scientifiques n'ont-ils pas trouvé un " chaînon manquant " entre les singes et nous ?
Parce qu'il n'existe pas. Les chimpanzés (et les autres singes) n'ont pas évolué pour devenir humains. Les deux lignées descendent d'un ancêtre commun et ont suivi chacune leur propre chemin. La vraie question est de savoir qui était cet ancêtre commun, ce géniteur manquant des chimpanzés et des humains. Nous ne le savons pas encore.
L'évolution est-elle terminée pour nous et les autres singes ?
Certainement pas. Les humains continuent d'évoluer, mais pour l'instant cette évolution est guidée autant par notre culture et la technologie, que nous avons inventées, que par notre biologie. Les autres animaux, dont les singes, continuent également leur évolution, et en particulier à notre époque à cause des énormes changements provoqués dans leur environnement par les humains.

# data[].attributes.attachment_link.description
La découverte d' Homo naledi, dernière branche en date de notre arbre généalogique, ravive le débat sur l'évolution humaine, et impose un rappel des bases que nous avons tous oubliées. Voici les réponses à quelques questions courantes. Pourquoi les scientifiques sont-ils certains que l'évolution humaine a bien eu lieu ?

# data[].attributes.attachment_link.readable_text
TED Members help billions of people worldwide access inspiring ideas. Plus, they get exclusive benefits like invite-only events with speakers. Join today for a brighter future - and a better you.

# data[].attributes.attachment_link.title
Prosanta Chakrabarty: Four billion years of evolution in six minutes

# data[].attributes.attachment_link.description
Did humans evolve from monkeys or from fish? In this enlightening talk, ichthyologist and TED Fellow Prosanta Chakrabarty dispels some hardwired myths about evolution, encouraging us to remember that we're a small part of a complex, four-billion-year process -- and not the end of the line. "We're not the goal of evolution," Chakrabarty says.

# data[].attributes.attachment_link.title
Ancient jaw suggests humans left Africa earlier than thought

# data[].attributes.attachment_link.description
A fossil jaw found in a cave in Israel is at least 177,000 years old. The scientists who found it think it shows humans left Africa much earlier than thought.

# data[].attributes.attachment_link.title
The Evolution Of Humans | Science Full Documentary

# data[].attributes.attachment_link.title
Human Evolution: The Complete Story Of Our Existence