On November 16, 2006, Science Daily published an interview that suggested that Neanderthals and ancient humans probably did not interbreed. Edward M. Rubin, director of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and the Joint Genome Institute (JGI), sequenced a fraction (0.00002) of genomic nuclear DNA (nDNA) from a 38,000-year-old Vindia Neanderthal femur bone. They calculated the common ancestor to be about 353,000 years ago, and a complete separation of the ancestors of the species about 188,000 years ago. Their results show the genomes of modern humans and Neanderthals are at least 99.5% identical, but despite this genetic similarity, and despite the two species having coexisted in the same geographic region for thousands of years, Rubin and his team did not find any evidence of any significant crossbreeding between the two. Rubin said, “While unable to definitively conclude that interbreeding between the two species of humans did not occur, analysis of the nuclear DNA from the Neanderthal suggests the low likelihood of it having occurred at any appreciable level.”
A main proponent of the interbreeding hypothesis is Erik Trinkaus of Washington University. In a 2006 study published in Proceedings of the National Academy of Sciences, Trinkaus and his co-authors report a possibility that Neanderthals and humans did interbreed. The study claims to settle the extinction controversy; according to researchers, the human and neanderthal populations blended together through sexual reproduction. Trinkaus states, “Extinction through absorption is a common phenomenon.” and “From my perspective, the replacement vs. continuity debate that raged through the 1990s is now dead”. Erik Trinkaus thinks he sees evidence of interbreeding between Neanderthals and modern humans in some fossils like the 24,500-year-old skeleton of a child found in Lagar Velho in Portugal.
Recently, Richard E. Green et al. from Max Planck Institute for Evolutionary Anthropology published the full sequence of Neanderthal mitochondrial DNA (mtDNA) and suggested that “Neandertals had a long-term effective population size smaller than that of modern humans.” While reporting in Nature Journal about the same publication, James Morgan asserted that the mtDNA sequence contained clues that Neanderthals lived in “small and isolated populations, and probably did not interbreed with their human neighbours.”
http://en.wikipedia.org/wiki/Neandertal_man
Well then, the neanderthal thing must not be the “root cause” of the stay behinds in Europe waffling so consistently between abject passivity and total militant authoritarianism.
I will now update my assumption off the neander thing and onto “must be something in the water”.
The first question is whether or not Cro-Magnon, or the early modern people who migrated into Europe, and Neanderthal people could actually mate and produce healthy, viable offspring. We may not know the answer to that for a long time (if ever). If they could mate, then I would find it hard to believe that they did not, given that the two groups overlapped each other in time and geography. That would explain why certain Neanderthal-like traits still persist in the European gene pool.