Further fine-tuning of the genetic history of more recent Neaderthals

These GEITP pages have often discussed the evolution of modern human species and their migrations Out of Africa. In Southeast Asia, Neanderthals (Homo neanderthalensis) diverged from the modern human (Homo sapiens) lineage ~600,000 years ago. This diagram (shared previously on these pages) should be helpful to “visualize” the various branches of the Homo tree [https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2016/neanderthals.jpg]:
Interbreeding between Neanderthals and early modern humans appears likely to have occurred in the time from less than ~200,000 years ago, almost up until the time of Neaderthal extinction (which occurred in what is now Europe, ~25,000 years ago). In the genomes of present-day non-Africans, this interbreeding has resulted in ~2% Neanderthal DNA. [As previously discussed, Neanderthal DNA can have both beneficial and undesirable effects on the health of modern humans.]

Little is known about the diversity of late Neanderthal populations across Europe and western Asia shortly before their disappearance, however, or about their relationship to the population that admixed with early modern humans. Only a few Neanderthal skeletons have been identified with a sufficiently high content of endogenous DNA (i.e. satisfactorily low levels of microbial and human DNA contamination) to allow analysis of larger parts of their genomes –– limiting our ability to study their genetic history.

In the attached report, authors used hypochlorite treatment of as little as 9 mg of bone or tooth powder(!!) –– to generate ample genomic coverage of five Neanderthals who had lived around 39,000 to 47,000 years ago, thereby doubling the number of Neanderthals for which genome sequences are available. Genetic similarity among late Neanderthals is well predicted by their geographical location, and by the comparison to the genome of an older Neanderthal from the Caucasus Mountains. This indicates that a population turnover is likely to have occurred, either in the Caucasus or throughout Europe, towards the end of Neanderthal history. Authors found that the bulk of Neanderthal gene flow into early modern humans originated from one or more source populations that diverged from the Neanderthals that were studied in Europe –– at least 70,000 years ago, but after they had diverged from a previously sequenced Neanderthal from Siberia ~150,000 years ago. Although four of the Neanderthals studied herein post-date the putative arrival of early modern humans into Europe, authors did not detect any recent gene flow from early modern humans into the Homo sapiense ancestry.

Nature 29 Mar 2o18; 555: 652–656

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