Еvery Thursday, Laboratory Equipment features a Scientist of the Week, chosen from the science industry’s latest headlines. This week’s scientist is Tom Higham from the Univ. of Oxford. He and a team found that Neanderthals went extinct in Europe much earlier than previously thought.
Q: What made you interested in dating Neanderthal bones?
A: I am interested in working out when Neanderthals went extinct and how long they overlapped with the earliest anatomically modern humans in places like Europe. The European archaeological record is one of the best examples of the extinction of a human species, and we are interested in knowing how it happened and when. Directly radiocarbon human bone is important, because it gives us a direct date for the person, not for the archaeological layer in which the bone was found. Sometimes bone can move around in sites, so a direct date is very useful where possible.
Q: What are the future implications of your research and findings?
A: The challenge for radiocarbon dating is in dating material that is close to the measurement limit, from around 30,000 BP (years before present) to the maximum determinable age at ~50,000 BP. We have found that there are major problems with previous dates obtained in the 1970s on because they often underestimate the true age. This is due to small amounts of unremoved contamination. One percent modern carbon in a sample is enough to skew the age of a bone by several thousand years. Our research has shown that sadly many previous dates are not accurate. New work is required, and we have been undertaking this over the last few years using new chemistry approaches.
Q: What was the most surprising thing you found in your research?
A: Some of the results we have obtained on Neanderthal bones have been very interesting. We have redated several bones that were amongst the youngest Neanderthals in the world. At Vindija Cave in Croatia, for example, two Neanderthal bones were previously dated at around 28,000 BP. We redated them using improvement chemical pretreatment methods to remove contaminants and pushed the ages back around 5,000 years. A similar thing happened in the Russian North Caucasus at a site called Mezmaiskaya, where we were able to show a similar pattern. In Spain we dated a sample of bone from a Neanderthal site that was around 32,000 BP and produced an age that indicated it was more than 50,000 BP. This is all the contribution of new chemistry methods on the extraction and purification of bone collagen, which is what we analyze.
Q: What is the take home message of your research and results?
A: Improved chemical preparation and measurement methods are the key in any scientific research. In archaeology the bone we analyze is ancient and the collagen in it has become degraded and is poorly preserved. In addition, in modern bone the isotope of radiocarbon is present at 10-12 percent, but by 40,000 years the amount is less than one percent of that. This makes radiocarbon dating very challenging. With improved methods, however, we have been able to provide results that are reliable. These dates are the key in deciphering what happened in the past, and in this case when Neanderthals became extinct and how much time we overlapped with them.
Q: What new technologies did you use in your lab during your research?
A: We are using high performance liquid chromatography to separate individual amino acids in bone collagen and isolate hydroxproline. This amino acid is quite specific to mammalian collagen and so extracting and radiocarbon dating just this amino is a virtual guarantee that contamination has been eliminated. This technique is rather like the gold standard of radiocarbon dating of bone now, and we are now applying it to cases where bones are very contaminated and hard to date using other less refined methods.
Q: What is next for you and your research?
A: I have recently been awarded a €2.5 million European Research Council grant to investigate and date sites across Eurasia where Neanderthals and early modern humans once lived. This will allow us to explore the extinction process and look at how modern humans came out of Africa and colonized the Old World. Everyone today outside Africa is descended from these people. We are researching the origins of humanity, from around 70,000 years ago up to the time at which these first people reached western Europe and eastern Siberia.