Bones of contention in fossil world may be thing of the past
New tool kit that uses DNA mutations could change the way we date skeletons and shed light on ancient cultures
Scientists in paleontology often find themselves at loggerheads over the age of a skeleton, with even the most advanced technology sometimes producing different data.
The most recent “bones of contention” were those of Homo naledi, the curious species found in a deep and dark chamber in the Cradle of Humankind, about 50km from Johannesburg, in 2015.
At first estimated to be about two million years old, it later emerged that the fossils were only 250,000 years old.
Now, scientists have discovered a new tool kit which, though still in its early phase of development, could change the way we date skeletons and thus shed much more light on our own ancestry.
Current methods rely on a variety of tools including dating the sedimentary rock in which fossils are found and using radiocarbon dating on the bones themselves.
The latter looks at how much radiocarbon is present in the fossil since, after a creature dies, the radiocarbon in its body decays into nitrogen. By calculating how much remains, an age can be inferred when compared with amounts of carbon-12, which doesn’t decay.This is a very useful method and is also considered to be highly accurate. But, it is also very sensitive and thus, sometimes, even the tiniest mistake in the methodology can lead to a vastly incorrect reading. Also, sometimes there isn’t enough radiocarbon present in the fossils to get a reading at all.
The new method, called Time Population Structure, can “calculate the mixtures of DNA deriving from different time periods to estimate its definitive age”. In other words, it uses mutations to predict time in order to date the ancient DNA.
The method was inspired by the Geographic Population Structure which tracks DNA mutations over different geographical settings.
Lead researcher Dr Umberto Esposito, from the University of Sheffield, on Monday told attendees at the annual meeting of the European Society of Human Genetics (ESHG) how his research could change the face of paleogenetics.
“This introduces a completely new approach to dating. At this point, in its embryonic state, TPS has already shown that its results are very similar to those obtained with traditional radiocarbon dating,” he said.
So far the average difference in age from fossils from about 45,000 years ago has been about 800 years when the results of radiocarbon dating have been compared with the new TPS.By paleontology standards, that is minuscule.
“This study adds a powerful instrument to the growing toolkit of paleogeneticists that can contribute to our understanding of ancient cultures, most of which are currently known from archaeology and ancient literature,” he said.
If you compared it to forensic investigations, it would be like a new and entirely different method of testing that could check the veracity of what the fingerprints and bloodstain patterns, for example, were telling you.
It doesn’t mean those fingerprints and bloodstain patterns are no longer used – there is just a wider range of methods that can confirm or challenge their results, and it also means that if those pieces of evidence were not available, there would be another accurate method in their place to help figure out how the crime took place.
This is the same: TPS augments radiocarbon testing, it doesn’t replace it.
So why do the ages of skeletons matter so much?
As a species, we’re innately fascinated by our own genetic history, always asking if any newly discovered species is part of our lineage or not. On top of that, we’re obsessed with our own migration routes, and a fundamental key to that treasure chest of information comes down to dating the bones of our possible ancestors.
In the words of Esposito, “the study of genetic data allows us to uncover long-lasting questions about migrations and population mixing in the past. In this context, dating ancient skeletons is of key importance for obtaining reliable and accurate results”.
Health research will benefit too: the study of genetic disorders is “closely tied up with questions of ancestry and population stratification”, so being able to analyse the homogeneity of populations is of vital importance to epidemiologists.
ESHG conference chairperson Professor Joris Veltman said: “This is another example of the power of modern genomics technologies to assist in helping us understand where we come from, how the journeys of our forefathers have helped shape our current genome, and how this now impacts our current abilities and weaknesses, including risks of disease.”