We’ve been quite limited by our ancient DNA of Neanderthals due to limited sample size from the fossil record and then compounded with degradation and contamination of DNA. Last week, Nature, published a fantastic article ultimately from Svante Pääbo and Janet Kelso on a novel way to extract more DNA from less fossil sample; using ClO−, on 9 mg of bone to generate up to 2.7x genomic coverage of five Neanderthals from approx. 39,000 to 47,000 years ago. This is the highest resolution coverage we have on the most number of Neanderthals and this is in particular what makes this such a fantastic paper… One that you should pay attention to if you are interested in ancient DNA and paleo-genetics.
Near Russia’s border with Georgia, Mezmaiskaya Cave offered shelter to Neanderthals for tens of thousands of years. Two of the individuals were not analyzed before and came from this cave. The other sites caves in Belgium, France, and lastly from Croatia were sequenced before. Some interesting population patterns have been figured out. For example, Mezmaiskaya 1 and 2 were not closely related. Instead Mezmaiskaya 2 seemed to be more closely related to the western Croatian, Belgian, and French Neanderthals than to Mezmaiskaya 1. This opens a door to suggest Eastern European Neanderthals were wiped out at some point . They were replaced by an influx of western Neanderthals. Perhaps extreme cold periods in northern Europe that occurred between the times of Mezmaiskaya 1 and 2 occupation may been the basis of a local extinction of Neanderthal populations there.
These five Neanderthals occupied Europe late, at a time when modern humans already moved in too. So did these later Neanderthals interbreed with modern humans? No, say the authors, they could not find any recent gene flow from early modern humans to late Neanderthals. The Neanderthal gene flow that we know has occurred likely happened before these five individuals were alive… Sometime between 70,000 and 150,000 years ago.
I consider this a hallmark paper, because they were able to extract more high quality DNA from less sample. We now have new information about the changes in Neanderthal populations and when they mixed with modern humans. And we can now answer more questions about ancient Neanderthal and human populations.