When the draft sequence of the Neandertal genome was analyzed it turned out that there was little difference across non-Africans in their proportion of admixture from this other human lineage. It was a rather strange finding as Neandertals seem to have flourished from Europe to the Altai, and from the ice sheets to the fringes of the Middle East. If Papuans had Neandertal admixture the logical conclusion was that that had to occur in the Middle East. Additionally, if Europeans didn’t have much more Neandertal admixture than Papuans, that means that after the initial absorption the modern humans simply swept the field as they pushed north and west.
But there’s a little problem here: the archeology indicates that Neandertals survived for nearly ten thousand years in Europe after the first arrival of moderns. So the necessary conclusion granting all the above is that after the initial hybridization some barrier prevented further leakage of Neandertal genes into Europeans (or, perhaps modern Europeans descend from recently arrived Middle Eastern farmers who lack the full Neandertal complement of Paleolithic Europeans?).
A new paper in PNAS overturns these paradoxes by re-dating the last Neandertals, allowing them to melt away rather quickly ~40,000 years B.P., just as modern humans were sweeping across Eurasia. Revised age of late Neanderthal occupation and the end of the Middle Paleolithic in the northern Caucasus:
Advances in direct radiocarbon dating of Neanderthal and anatomically modern human (AMH) fossils and the development of archaeostratigraphic chronologies now allow refined regional models for Neanderthal–AMH coexistence. In addition, they allow us to explore the issue of late Neanderthal survival in regions of Western Eurasia located within early routes of AMH expansion such as the Caucasus. Here we report the direct radiocarbon (14C) dating of a late Neanderthal specimen from a Late Middle Paleolithic (LMP) layer in Mezmaiskaya Cave, northern Caucasus. Additionally, we provide a more accurate chronology for the timing of Neanderthal extinction in the region through a robust series of 16 ultrafiltered bone collagen radiocarbon dates from LMP layers and using Bayesian modeling to produce a boundary probability distribution function corresponding to the end of the LMP at Mezmaiskaya. The direct date of the fossil (39,700 ± 1,100 14C BP) is in good agreement with the probability distribution function, indicating at a high level of probability that Neanderthals did not survive at Mezmaiskaya Cave after 39 ka cal BP (“calendrical” age in kiloannum before present, based on IntCal09 calibration curve). This challenges previous claims for late Neanderthal survival in the northern Caucasus. We see striking and largely synchronous chronometric similarities between the Bayesian age modeling for the end of the LMP at Mezmaiskaya and chronometric data from Ortvale Klde for the end of the LMP in the southern Caucasus. Our results confirm the lack of reliably dated Neanderthal fossils younger than ∼40 ka cal BP in any other region of Western Eurasia, including the Caucasus.
Nick Wade gets some quotes from the principals in The New York Times. I found this part amusing though:
Richard Klein, a paleoanthropologist at Stanford University, said Dr. Higham’s re-dating was “compelling” and fit with his own view that “modern humans were technologically and intellectually far superior to the Neanderthals.” This, he said, “would have allowed them to spread very rapidly and to precipitate the extinction of the Neanderthals almost immediately on contact.”
Klein would think so, he edited the paper in PNAS!