View Full Version : new paper on neanderthals

jose luis
16-03-20, 19:41

We sequenced the genome of a Neandertal from Chagyrskaya Cave in the Altai Mountains, Russia, to 27-fold genomic coverage. We estimate that this individual lived ~80,000 years ago and was more closely related to Neandertals in western Eurasia (1,2) than to Neandertals who lived earlier in Denisova Cave (3), which is located about 100 km away. About 12.9% of the Chagyrskaya genome is spanned by homozygous regions that are between 2.5 and 10 centiMorgans (cM) long. This is consistent with that Siberian Neandertals lived in relatively isolated populations of less than 60 individuals. In contrast, a Neandertal from Europe, a Denisovan from the Altai Mountains and ancient modern humans seem to have lived in populations of larger sizes. The availability of three Neandertal genomes of high quality allows a first view of genetic features that were unique to Neandertals and that are likely to have been at high frequency among them. We find that genes highly expressed in the striatum in the basal ganglia of the brain carry more amino acid-changing substitutions than genes expressed elsewhere in the brain, suggesting that the striatum may have evolved unique functions in Neandertals.

jose luis
17-03-20, 17:12
100,000 years of gene flow between Neandertals and Denisovans in the Altai mountains


The Siberian Altai mountains have been intermittently occupied by both Neandertals and Denisovans, two extinct hominin groups. While they diverged at least 390,000 years ago, later contacts lead to gene flow from Neandertals into Denisovans. Using a new population genetic method that is capable of inferring signatures of admixture from highly degraded genetic data, I show that this gene flow was much more widespread than previously thought. While the two earliest Denisovans both have substantial and recent Neandertal ancestry, I find signatures of admixture in all archaic genomes from the Altai, demonstrating that gene flow also occurred from Denisovans into Neandertals. This suggests that a contact zone between Neandertals and Denisovan populations persisted in the Altai region throughout much of the Middle Paleolithic. In contrast, Western Eurasian Neandertals have little to no Denisovan ancestry. As I find no evidence of natural selection against gene flow, this suggests that neutral demographic processes and geographic isolation were likely major drivers of human differentiation.

18-03-20, 09:00
I'm a bit sceptical.
The outcome is a bit surprising.
E.g. : the dating of Chagyrskaya is totally differented from what I've learned.
The papers aren't peer reviewed.

jose luis
07-04-20, 10:17
Multiple Archaic Introgression Events, Including from Altai Neanderthal Lineage


The time, extent, and genomic impact of the introgressions from archaic humans into ancestors of extant human populations remain one of the most exciting venues of population genetics research in the last decade. Several studies have shown population-specific signatures of introgression events from Neanderthals, Denisovans, and potentially other unknown hominin populations in different human groups. Moreover, it was shown that these introgression events may have contributed to phenotypic variation in extant humans, with biomedical and evolutionary consequences. In this study, we present a comprehensive analysis of the unusually divergent haplotypes in the Eurasian genomes and showed that they can be traced back to multiple introgression events. In parallel, we document hundreds of deletion polymorphisms shared with Neanderthals. A locus-specific analysis of one such shared deletion suggests the existence of a direct introgression event from the Altai Neanderthal lineage into the ancestors of extant East Asian populations. Overall, our study is in agreement with the emergent notion that various Neanderthal populations contributed to extant human genetic variation in a population-specific manner.

jose luis
23-04-20, 10:25
The nature of Neanderthal introgression revealed by 27,566 Icelandic genomes


Human evolutionary history is rich with the interbreeding of divergent populations. Most humans outside of Africa trace about 2% of their genomes to admixture from Neanderthals, which occurred 50–60 thousand years ago1. Here we examine the effect of this event using 14.4 million putative archaic chromosome fragments that were detected in fully phased whole-genome sequences from 27,566 Icelanders, corresponding to a range of 56,388–112,709 unique archaic fragments that cover 38.0–48.2% of the callable genome. On the basis of the similarity with known archaic genomes, we assign 84.5% of fragments to an Altai or Vindija Neanderthal origin and 3.3% to Denisovan origin; 12.2% of fragments are of unknown origin. We find that Icelanders have more Denisovan-like fragments than expected through incomplete lineage sorting. This is best explained by Denisovan gene flow, either into ancestors of the introgressing Neanderthals or directly into humans. A within-individual, paired comparison of archaic fragments with syntenic non-archaic fragments revealed that, although the overall rate of mutation was similar in humans and Neanderthals during the 500 thousand years that their lineages were separate, there were differences in the relative frequencies of mutation types—perhaps due to different generation intervals for males and females. Finally, we assessed 271 phenotypes, report 5 associations driven by variants in archaic fragments and show that the majority of previously reported associations are better explained by non-archaic variants.