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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