The journal Science has a blurb by Michael Balter on new dating of Neandertal remains by Thomas Higham. He writes:
These techniques have been used on the infant Neandertal remains from Mezmaiskaya Cave in Russia. They conclude that the overlap between Neandertals and modern humans in the region was very short. Balter continues:
For the past several years, radiocarbon dating expert Thomas Higham of the University of Oxford in the United Kingdom has been working with researchers all over Europe to improve the accuracy of radiocarbon dating at prehistoric sites. The technique relies on the radioactive isotope carbon-14, whose radioactivity diminishes over time in a predictable manner, allowing researchers to calculate the age of ancient human sites using charcoal from fires or the bones of the prehistoric humans themselves. But ancient carbon sources can easily become contaminated with more recent organic material, making prehistoric sites appear to be much younger than they really are.Higham and his Oxford colleagues have developed several techniques, including “ultra-filtration” of dating samples, to remove more recent carbon. The results are leading to a reevaluation of radiocarbon dates all over prehistoric Europe.
Neandertals and modern humans were probably like passing strangers, [Ron] Pinhasi says. “At this stage” of this ongoing research, he says, the results “do not support any major overlap between Neandertals and modern humans” much after 40,000 years ago, at which time Neandertals were probably going extinct.This is, of course, in sharp contrast to the remains in Portugal at Lagar Velho as well as those of Zafarraya, both of which date to between 26 and 28 ky BP. It may be, as Jan Simek once said “in this valley there was probably continuity between Neandertals and modern humans. Two valleys over, there may have been replacement.” It is certain that the transition was complex and involved two groups (species?) that were very similarly adapted to the landscape.