Dating edate internet

Obviously individuals and populations exhibit genetic relationships to each other contingent upon the patterns of the variation of base pairs (A, C, G, and T) across the genomes of individuals, but there’s no reasonable way to comprehend this “by eye” when you’re talking about hundreds of thousands of markers.

In a way this is rigging the game; if you force the method to squeeze out particular numbers of populations it may act strangely.

But in this case we have prior expectations, so this number of populations is not unreasonable.

Above each bar plot represents an African American individual, with each fraction of shading an ancestral element.

The results from the PCA are reproduced nearly perfectly by this differing method.

The above plot is from Characterizing the admixed African ancestry of African Americans, a 2009 paper with 94 Africans of diverse geographic origins, 136 African Americans, and 38 European Americans.

They looked at 450,000 genetic variants (SNPs) per person (there are somewhat more than 10 million SNPs in the human genome).This is entirely reasonable when you consider that the vast majority of their ancestors were resident in the colonies before the Revolutionary War.Admixture events would have percolated throughout the genealogical tree in subsequent generations.Each individual then has a value position on the dimension, dependent on how that individual relates to the others.When you take multiple dimensions and transpose the data geometrically you quickly see population structure fall out of the data set.In his posts on this topic Ta-Nehisi repeatedly points to the real diversity in physical type and ancestry among African Americans, despite acknowledging implicitly the shared preponderant history.

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