This is the blog for GW students taking Human Evolutionary Genetics. This site is for posting interesting tidbits on: the patterns and processes of human genetic variation;human origins and migration; molecular adaptations to environment, lifestyle and disease; ancient and forensic DNA analyses; and genealogical reconstructions.

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Monday, February 17, 2020

Recovering signals of ghost archaic introgression in African populations



Most population genetic studies focus on Europeans and their ancestors. However, a recent study of four West African populations could provide us with a better understanding of African and early human archaic ancestry. Recently, Chen et al. used a new method to identify introgressed hominin sequences without a modern reference population. Their study aligns with Durvasula and Sankararaman, who recently applied a similar method to West African populations. They provide evidence of an archaic population who split from the ancestor of Neanderthals and modern humans 360 ka to 1.02 Ma before introgressing between 124 – 0 ka.

They specifically measure frequency distributions of derived SNP alleles. This theory is predicated upon the conditional site frequency spectrum (CSFS) being uniformally-distributed under neutral evolution with no gene flow. Durvasula and Sankararaman found that approximately 2-19% of West African ancestry derives from this archaic populati
on. They acknowledge that while they favor a single interbreeding event model, there was more realistically extended periods of low gene flow. In addition, they did find similar CSFS patterns in non-African populations from Beijing and Utah with European ancestry, suggesting that some level of archaic ancestry was shared between the divergence of African and non-African populations.

Joshua Porter – 02/18/2020 Potluck

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