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When exploring this elaboration, it is crucial to keep the following points in mind:

·        interfering with the ancestral remains discovered at Lake Mungo is a sensitive issue for the Ngiyampaa, the Mutthi Mutthi and the Paakantji Aboriginal people who are descendants of Mungo Lady and Mungo Man and custodians of the remains

·        in many cases, Aboriginal peoples’ view on how long they have lived in Australia, embodied in the Dreaming and Aboriginal Law, is that they have always lived in Australia.

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How Does Radiocarbon Dating Work? - Instant Egghead #28

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At least to the uninitiated, carbon dating is generally assumed to be a sure-fire way to predict the age of any organism that once lived on our planet. Without understanding the mechanics of it, we put our blind faith in the words of scientists, who assure us that carbon dating is a reliable method of determining the ages of almost everything around us. However, a little more knowledge about the exact ins and outs of carbon dating reveals that perhaps it is not quite as fool-proof a process as we may have been led to believe.

What is Carbon Dating?

At its most basic level, carbon dating is the method of determining the age of organic material by measuring the levels of carbon found in it. Specifically, there are two types of carbon found in organic materials: carbon 12 (C-12) and carbon 14 (C-14). It is imperative to remember that the material must have been alive at one point to absorb the carbon, meaning that carbon dating of rocks or other inorganic objects is nothing more than inaccurate guesswork.

All living things absorb both types of carbon; but once it dies, it will stop absorbing. The C-12 is a very stable element and will not change form after being absorbed; however, C-14 is highly unstable and in fact will immediately begin changing after absorption. Specifically, each nucleus will lose an electron, a process which is referred to as decay. This rate of decay, thankfully, is constant, and can be easily measured in terms of 'half-life'.

Half-life refers to the amount of time it takes for an object to lose exactly half of the amount of carbon (or other element) stored in it. This half-life is very constant and will continue at the same rate forever. The half-life of carbon is 5,730 years, which means that it will take this amount of time for it to reduce from 100g of carbon to 50g - exactly half its original amount. Similarly, it will take another 5,730 years for the amount of carbon to drop to 25g, and so on and so forth. By testing the amount of carbon stored in an object, and comparing to the original amount of carbon believed to have been stored at the time of death, scientists can estimate its age.

So what's the Problem?

Unfortunately, the believed amount of carbon present at the time of expiration is exactly that: a belief, an assumption, an estimate. It is very difficult for scientists to know how much carbon would have originally been present; one of the ways in which they have tried to overcome this difficulty was through using carbon equilibrium.

Equilibrium is the name given to the point when the rate of carbon production and carbon decay are equal. By measuring the rate of production and of decay (both eminently quantifiable), scientists were able to estimate that carbon in the atmosphere would go from zero to equilibrium in 30,000 - 50,000 years. Since the universe is estimated to be millions of years old, it was assumed that this equilibrium had already been reached.

However, in the 1960s, the growth rate was found to be significantly higher than the decay rate; almost a third in fact. This indicated that equilibrium had not in fact been reached, throwing off scientists' assumptions about carbon dating. They attempted to account for this by setting 1950 as a standard year for the ratio of C-12 to C-14, and measuring subsequent findings against that.

Has it Worked?

In short, the answer is... sometimes. Sometimes carbon dating will agree with other evolutionary methods of age estimation, which is great. Other times, the findings will differ slightly, at which point scientists apply so-called 'correction tables' to amend the results and eliminate discrepancies.

Most concerning, though, is when the carbon dating directly opposes or contradicts other estimates. At this point, the carbon dating data is simply disregarded. It has been summed up most succinctly in the words of American neuroscience Professor Bruce Brew:

"If a C-14 date supports our theories, we put it in the main text. If it does not entirely contradict them, we put it in a footnote. And if it is completely out of date, we just drop it."

What does this mean for Contemporary Carbon Dating?

Essentially, this means that carbon dating, though a useful tool, is not 100% reliable. For example, recently science teams at the British Antarctic Survey and Reading University unearthed the discovery that samples of moss could be brought back to life after being frozen in ice. The kicker? That carbon dating deemed the moss to have been frozen for over 1,500 years. Now, if this carbon dating agrees with other evolutionary methods of determining age, the team could have a real discovery on their hands. Taken alone, however, the carbon dating is unreliable at best, and at worst, downright inaccurate.

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At least to the uninitiated, carbon dating is generally assumed to be a sure-fire way to predict the age of any organism that once lived on our planet. Without understanding the mechanics of it, we...

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Indigenous rock shelter in Top End pushes Australia's human history back to 65,000 years

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Indigenous rock shelter in Top End pushes Australia's human history back to 65,000 years

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Genelle Weule for ABC Science and Felicity James for ABC Darwin

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Ancient Indigenous rock shelter rewrites Australia’s human history

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New excavations of a rock shelter near Kakadu National Park indicate humans reached Australia at least 65,000 years ago — up to 18,000 years earlier than previously thought.

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Radiocarbon dating supports Aboriginal occupation of South Australia for 29,000 years

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Radiocarbon dating supports Aboriginal occupation of South Australia for 29,000 years

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Published on the 15th July 2020 by ANSTO Staff

Key Points

Recent archaeological evidence led by Flinders University in collaboration with the River Murray and Mallee Aboriginal Corporation supports the Aboriginal occupation of the Riverland area in South Australia for 29,000 years

Research is part of a larger effort to understand how Aboriginal people adapted to climate change over millennia

Radiocarbon dating at ANSTO using accelerator mass spectrometry was used to acquire the ages of mussell shells from middens

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Radiocarbon dating supports Aboriginal occupation of South Australia for 29,000 years

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Radiocarbon dating at ANSTO has supported research that vastly extends the known timeline of the Aboriginal occupation of South Australia's Riverland region, as reported in new research led by Flinders University in collaboration with the River Murray and Mallee Aboriginal Corporation (RMMAC).

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Explainer: what is radiocarbon dating and how does it work?

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Explainer: what is radiocarbon dating and how does it work?

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Make no bones about it, radiocarbon dating has transformed our understanding of the past. Wessex Archaeology

Radiocarbon dating has transformed our understanding of the past 50,000 years. Professor Willard Libby produced the first radiocarbon dates in 1949 and was later awarded the Nobel Prize for his efforts.

Radiocarbon dating works by comparing the three different isotopes of carbon. Isotopes of a particular element have the same number of protons in their nucleus, but different numbers of neutrons. This means that although they are very similar chemically, they have different masses.

The total mass of the isotope is indicated by the numerical superscript. While the lighter isotopes ¹²C and ¹³C are stable, the heaviest isotope ¹⁴ C (radiocarbon) is radioactive. This means its nucleus is so large that it is unstable.

Over time ¹⁴C decays to nitrogen ( ¹⁴N). Most ¹⁴C is produced in the upper atmosphere where neutrons, which are produced by cosmic rays, react with ¹⁴ N atoms.

It is then oxidised to create ¹⁴CO ₂, which is dispersed through the atmosphere and mixed with ¹²CO ₂ and ¹³CO ₂. This CO ₂ is used in photosynthesis by plants, and from here is passed through the food chain (see figure 1, below).

Every plant and animal in this chain (including us!) will therefore have the same amount of ¹⁴C compared to ¹²C as the atmosphere (the ¹⁴C: ¹² C ratio).

Dating history

When living things die, tissue is no longer being replaced and the radioactive decay of ¹⁴C becomes apparent. Around 55,000 years later, so much ¹⁴ C has decayed that what remains can no longer be measured.

Radioactive decay can be used as a "clock" because it is unaffected by physical (e.g. temperature) and chemical (e.g. water content) conditions. In 5,730 years half of the ¹⁴ C in a sample will decay (see figure 1, below).

Therefore, if we know the ¹⁴C: ¹² C ratio at the time of death and the ratio today, we can calculate how much time has passed. Unfortunately, neither are straightforward to determine.

The amount of ¹⁴C in the atmosphere, and therefore in plants and animals, has not always been constant. For instance, the amount varies according to how many cosmic rays reach Earth. This is affected by solar activity and the earth's magnetic field.

Luckily, we can measure these fluctuations in samples that are dated by other methods. Tree rings can be counted and their radiocarbon content measured. From these records a " calibration curve " can be built (see figure 2, below).

A huge amount of work is currently underway to extend and improve the calibration curve. In 2008 we could only calibrate radiocarbon dates until 26,000 years. Now the curve extends (tentatively) to 50,000 years.

Dating advances

Radiocarbon dates are presented in two ways because of this complication. The uncalibrated date is given with the unit BP (radiocarbon years before 1950).

The calibrated date is also presented, either in BC or AD or with the unit calBP (calibrated before present - before 1950). The calibrated date is our "best estimate" of the sample's actual age, but we need to be able to return to old dates and recalibrate them because new research is continually used to update the calibration curve.

The second difficulty arises from the extremely low abundance of ¹⁴C. Only 0.0000000001% of the carbon in today's atmosphere is ¹⁴ C, making it incredibly difficult to measure and extremely sensitive to contamination.

In the early years of radiocarbon dating a product's decay was measured, but this required huge samples (e.g. half a human femur). Many labs now use an Accelerator Mass Spectrometer (AMS), a machine that can detect and measure the presence of different isotopes, to count the individual ¹⁴ C atoms in a sample.

This method requires less than 1g of bone, but few countries can afford more than one or two AMSs, which cost more than A$500,000. Australia has two machines dedicated to radiocarbon analysis, and they are out of reach for much of the developing world.

In addition, samples need to be thoroughly cleaned to remove carbon contamination from glues and soil before dating. This is particularly important for very old samples. If 1% of the carbon in a 50,000 year old sample is from a modern contaminant, the sample will be dated to around 40,000 years.

Because of this, radiocarbon chemists are continually developing new methods to more effectively clean materials. These new techniques can have a dramatic effect on chronologies. With the development of a new method of cleaning charcoal called ABOx-SC, Michael Bird helped to push back the date of arrival of the first humans in Australia by more than 10,000 years.

Establishing dates

Moving away from techniques, the most exciting thing about radiocarbon is what it reveals about our past and the world we live in. Radiocarbon dating was the first method that allowed archaeologists to place what they found in chronological order without the need for written records or coins.

In the 19th and early 20th century incredibly patient and careful archaeologists would link pottery and stone tools in different geographical areas by similarities in shape and patterning. Then, by using the idea that the styles of objects evolve, becoming increasing elaborate over time, they could place them in order relative to each other - a technique called seriation.

In this way large domed tombs (known as tholos or beehive tombs) in Greece were thought to predate similar structures in the Scottish Island of Maeshowe. This supported the idea that the classical worlds of Greece and Rome were at the centre of all innovations.

Some of the first radiocarbon dates produced showed that the Scottish tombs were thousands of years older than those in Greece. The barbarians of the north were capable of designing complex structures similar to those in the classical world.

Other high profile projects include the dating of the Turin Shroud to the medieval period, the dating of the Dead Sea Scrolls to around the time of Christ, and the somewhat controversial dating of the spectacular rock art at Chauvet Cave to c.38,000 calBP (c.32,000 BP) - thousands of years earlier than expected.

Radiocarbon dating has also been used to date the extinction of the woolly mammoth and contributed to the debate over whether modern humans and Neanderthals met.

But ¹⁴C is not just used in dating. Using the same techniques to measure ¹⁴ C content, we can examine ocean circulation and trace the movement of drugs around the body. But these are topics for separate articles.

If you'd like to learn more about radiocarbon dating, www.c14dating.com is an excellent starting point.
See more Explainer articles on The Conversation.

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Explainer: what is radiocarbon dating and how does it work?

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Radiocarbon dating has transformed our understanding of the past 50,000 years. Professor Willard Libby produced the first radiocarbon dates in 1949 and was later awarded the Nobel Prize for his efforts. Radiocarbon dating works by comparing the three different isotopes of carbon.

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Radiocarbon dating at ANSTO informs date of oldest known Aboriginal rock art

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Radiocarbon dating at ANSTO informs date of oldest known Aboriginal rock art

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Australia's Nuclear Science and Technology Organisation

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Radiocarbon dating at ANSTO informs date of oldest known Aboriginal rock art

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ANSTO’s world-class radiocarbon dating capabilities at the Centre for Accelerator Science have provided evidence of a 17,300-year-old painting of a kangaroo from the Kimberley region that pre-dates the Gwion Gwion style.

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Mungo Man: 42,000-year-old Aboriginal remains to be reburied

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Mungo Man: 42,000-year-old Aboriginal remains to be reburied

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The remains of Mungo Man carried in a casket made from a 5000-year-old red gum

The remains of 108 Aboriginal people who died about 42,000 years ago will be reburied in outback Australia, years after they were first dug up without permission.

These include the remains of Mungo Man, which was famously discovered in 1974 and helped rewrite Australia's history.

The decision comes after the federal government finalised a four-year-long formal assessment about the reburial.

But some indigenous groups claim they were not consulted in this process.

Between 1960 and 1980, there were a flurry of archaeological finds.

During this time, researchers found the remains of 108 Aboriginal individuals in Lake Mungo and Willandra lakes, part of the Willandra world heritage area, about 750km (470 miles) west of Sydney - including the remains of an aboriginal man who was dubbed Mungo Man.

At the time, his remains were the oldest evidence of humans living in Australia, and evidence of the first, recorded ceremonial burial - a sign that there had been a long history of civilisation, as early as 42,000 years ago.

That record was broken when another 65,000-year-old site was discovered elsewhere in 2017.

Lake Mungo, in Australia's Willandra region, is where the 42,000-year-old remains of indigenous Australians were found.

However the future of these ancient remains is still a matter of debate.

Campaigners say many remains, removed without permission, are yet to be returned - with some housed in museums overseas. In the case of Mungo Man, indigenous Australians said the removal of his remains caused great pain.

Mungo Man was finally returned to Mungo National Park, where he was found, in 2017, after being kept in storage at the Australian National University in Canberra.

In 2018, the Australian government decided to rebury all 108 remains - in what they described as an effort to accommodate the wishes of Aboriginal groups. On Wednesday, the government finally approved the reburial of the remains over the coming month, at 26 anonymous locations in national parks.

"Forty-two thousand years ago, Aboriginal people were living - and thriving - on the edge of what was then a rich lakeside. In the last four decades their remains have been removed, analysed, stored, and extensively investigated in the interests of western science.", Federal Environment Minister Sussan Ley said.

While the government asserted that they had listened to the local Aboriginal community, some of the community members feel let down by the process.

Local papers, quoting some locals, said they felt "bitter disappointment" as not all the owners of the remains were consulted.

Michael Young, a Paakantyi man from the community, said the central government continued to make decisions without them, according to an ABC News report.

"It is our place. It is our identity."

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Mungo Man: 42,000-year-old Aboriginal remains to be reburied

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The remains of 108 Aboriginal people will be reburied in anonymous sites in national parks.

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Isotope analysis helps tell the stories of Aboriginal people living under early colonial expansion

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Isotope analysis helps tell the stories of Aboriginal people living under early colonial expansion

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Isotope analysis helps tell the stories of Aboriginal people living under early colonial expansion

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Research conducted with Gkuthaarn and Kukatj community members helps paint a picture of the lives of eight young Aboriginal people who lived during early colonial expansion.

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Human occupation of northern Australia by 65,000 years ago

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Human occupation of northern Australia by 65,000 years ago

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Aboriginal inhabitants of Madjedbebe, northern Australia used different ways to adapt to environmental change

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Aboriginal inhabitants of Madjedbebe, northern Australia used different ways to adapt to environmental change

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Australia's Nuclear Science and Technology Organisation

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Aboriginal inhabitants of Madjedbebe, northern Australia used different ways to adapt to environmental change

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ANSTO has contributed to research that indicated that Aboriginal people had a broad diet and intensive plant processing technologies, allowing them to respond to changes in climate, sea level and vegetation over the last (circa) 65,000 years.