October 19, 2012

Neandertals and modern humans may not have met in the southern Caucasus

There have been some recent indications that modern West Eurasians might not have precisely equal amounts of Neandertal ancestry, and that these differences may have been accented during prehistory. One possible explanation for this might be the fact that as modern humans expanded in Eurasia, they encountered different concentrations of Neandertals, and, in some places no Neandertals at all.

This hypothesis may be better resolved once a high coverage Neandertal genome is published, to complement the recent publication of the Denisova genome, as well as the new Altai Neandertals recently announced.

Journal of Human Evolution doi:dx.doi.org/10.1016/j.jhevol.2012.08.004

New chronology for the Middle Palaeolithic of the southern Caucasus suggests early demise of Neanderthals in this region

R. Pinhasi et al.

Neanderthal populations of the southern and northern Caucasus became locally extinct during the Late Pleistocene. The timing of their extinction is key to our understanding of the relationship between Neanderthals and anatomically modern humans (AMH) in Eurasia. Recent re-dating of the end of the Middle Palaeolithic (MP) at Mezmaiskaya Cave, northern Caucasus, and Ortvale Klde, southern Caucasus, suggests that Neanderthals did not survive after 39 ka cal BP (thousands of years ago, calibrated before present). Here we extend the analysis and present a revised regional chronology for MP occupational phases in western Georgia, based on a series of model-based Bayesian analyses of radiocarbon dated bone samples obtained from the caves of Sakajia, Ortvala and Bronze Cave. This allows the establishment of probability intervals for the onset and end of each of the dated levels and for the end of the MP occupation at the three sites.

Our results for Sakajia indicate that the end of the late Middle Palaeolithic (LMP) and start of the Upper Palaeolithic (UP) occurred between 40,200 and 37,140 cal BP. The end of the MP in the neighboring site of Ortvala occurred earlier at 43,540–41,420 cal BP (at 68.2% probability). The dating of MP layers from Bronze Cave confirms that it does not contain LMP phases.

These results imply that Neanderthals did not survive in the southern Caucasus after 37 ka cal BP, supporting a model of Neanderthal extinction around the same period as reported for the northern Caucasus and other regions of Europe. Taken together with previous reports of the earliest UP phases in the region and the lack of archaeological evidence for an in situ transition, these results indicate that AMH arrived in the Caucasus a few millennia after the Neanderthal demise and that the two species probably did not interact.



Anonymous said...

Ortvale Klde ("Two Eyes Cave") is a shallow cave located in the footslopes of the Caucasus Mountains of the republic of Georgia. It was occupied by hominins-Neanderthals and Modern humans-between about 50,000 and 21,000 years ago, during the so-called Middle Paleolithic and Upper Paleolithic periods. Hominin remains are rarely found in Georgia, and as a result their sites are identified by the set of stone tools they used-called lithic assemblages by archaeologists. Neanderthals had a fairly limited stone tool assemblage with tools used for many different purposes. Early Modern humans made a wider variety of stone tools, some made for specific purposes as well as tools of bone and antler. At Ortvale Klde the Neanderthal tool kit included elongated blades and scrapers for general use.

eurologist said...

The authors still pose that there may have been a ~5,000 year overlap between AMHs and Neanderthals overall - but it looks like in most regions, Neanderthals locally disappeared when AMHs arrived (while the latter strongly grew in numbers).

I am not surprised that there is little evidence for regional co-habitation. If Neanderthals left, died from diseases, intermixed, or simply were outnumbered, this would have taken place in a manner of at most a couple of hundred years (regionally), and would have left few traces in the record.

AMHs were highly mobile and used tents and other structures - they might have only re-discovered many of the caves after a long time, which would explain the hiatus in occupation.

andrew said...

I am deeply skeptical of a Neanderthal extinction followed by AMH expansion into vacant territory theory. A scenario where the arrival of AMHs causes a weakened local Neanderthal population to retreat or go extinct is far more plausible given the near universal close coincidence of AMH arrival and Neanderthal disappearance locally.

terryt said...

"these results indicate that AMH arrived in the Caucasus a few millennia after the Neanderthal demise and that the two species probably did not interact".

The assumption seems to be that both the last Neanderthal presence and the first modern human presence have been discovered. Surely that is an extremely unlikely assumption to adopt.