Neanderthals were a group of archaic hominins that occupied most of Europe and parts of Western Asia from roughly 30-300 thousand years ago (Kya). They coexisted with modern humans during part of this time. Previous genetic analyses that compared a draft sequence of the Neanderthal genome with genomes of several modern humans concluded that Neanderthals made a small (1-4%) contribution to the gene pools of all non-African populations. This observation was consistent with a single episode of admixture from Neanderthals into the ancestors of all non-Africans when the two groups coexisted in the Middle East 50-80 Kya. We examined the relationship between Neanderthals and modern humans in greater detail by applying two complementary methods to the published draft Neanderthal genome and an expanded set of high-coverage modern human genome sequences. We find that, consistent with the recent finding of Meyer et al. (2012), Neanderthals contributed more DNA to modern East Asians than to modern Europeans. Furthermore we find that the Maasai of East Africa have a small but significant fraction of Neanderthal DNA. Because our analysis is of several genomic samples from each modern human population considered, we are able to document the extent of variation in Neanderthal ancestry within and among populations. Our results combined with those previously published show that a more complex model of admixture between Neanderthals and modern humans is necessary to account for the different levels of Neanderthal ancestry among human populations. In particular, at least some Neanderthal-modern human admixture must postdate the separation of the ancestors of modern European and modern East Asian populations.
By using the high coverage Denisova genome, we are able to show that the admixture rate into East Asians is 40% higher than into Europeans.
|Figure S1: Box plot of the D-statistics for Analyses A and B for the set (Afr, X), where X was any of the non-African populations,
CEU or TSI (Europeans, green), CHB or JPT (East Asians, blue), or GIH (South Asian, pink) (PDF, 222 KB).
- Founder effect among East Asians, known to have less overall genetic diversity and suspected to have undergone some extra (mild?) bottleneck at their ancient origins.
- Low-level African (and surely also early OoA residuals from West Asia) admixture among West Eurasians, notably Tuscans (TSI) in these samples but also to some extent all Europeans (incl. CEU). This has the effect of increasing genetic diversity but also of slightly diluting Neanderthal admixture. The control here are Indians (GIH), which show slightly more Neanderthal admixture than Europeans (but are still closer to these than to East Asians also in this aspect).
- On some details of the Neanderthal genome draft (Leherensuge 2010, when I noticed that Chinese, but not Japanese, samples looked like having slightly more admixture)
- Splitting hairs on the Neanderthal affinity, questioning if the slight greater Neanderthal admixture detected by John Hawks among Europeans (the opposite of what is claimed here) was actually meaningful at all.
- East Asians now claimed to be more Neanderthal than Europeans (prelude of this paper in a sense)
- Intriguing North African Neanderthal admixture paper