The cohabitation of Neandertals and modern humans in Europe about 35,000 years ago has stimulated considerable debate regarding hypothetical admixture. Recently, sequences of the hypervariable region-1 (HVR-1) of mitochondrial DNA (mtDNA) from 9 Neandertal specimens dated between 29,000 and 42,000 years ago from dispersed locations have revealed the genetic diversity of Neandertals around the time of the cohabitation 1, 2, 3 and 4. The genetic signatures before and after contact with modern humans were found to be similar. They fall outside the range of modern human genetic diversity and show no specific affinity with modern or Paleolithic Europeans . Such observations are generally taken as strong evidence for the ‘Rapid replacement’ model for the origin of modern humans 4 and 6, though further evidence is needed to completely exclude admixture .
Remember, this is mitochondrial DNA, a genealogy on one locus can tell you only so much, and one should be cautious about conflating it with demographic history….
The “money shot” below the fold:
The pairwise distance distributions within humans, as well as between humans and Neandertals, are closer and overlap more extensively for more recent Neandertals (p < 0.001) than for the Scladina specimen (Figure 2). While the diversity of the more recent Neandertals is similar to that of modern humans worldwide, the sequence from Scladina reveals that more divergent Neandertal haplotypes existed before 42,000 years ago. This could suggest that Neandertals experienced genetic drift as demographic bottlenecks eliminated the phylogenetically more recent (i.e. less expanded) haplotypes from populations. Consequently, the most likely conserved Neandertal haplotypes could also be the phylogenetically most ancient (i.e. the most closely related to the common ancestor of modern humans and Neandertals). This could explain the shift towards modern human pairwise distributions observed between 100,000 and 40,000 years ago. Whatever this shift should be related to cohabitation, climatic changes, or any subdivision of populations, the Scladina sequence has revealed that the genetic diversity of Neandertals has been underestimated. Thus, more Neandertal sequences than the six presently available and longer than 100 bp are needed to fully understand the extent of the past diversity of Neandertals.
Update: As always, John Hawks has more.