On the other hand I have always appreciated that a benefit of this injustice to the methods which make insight possible is that those without academic access can actually bite into the meat of the researcher’s mode of thought. That has to end now, because the authors have finally released a software package which implements the statistics, ADMIXTOOLS.
I plan to use it in the near future, and it is generally best if you understand the underlying mechanisms of a software package if you are at the bleeding end of analytics.
Subsequent mating between peoples of neighboring regions, resulting in isolation-by-distance (LAO et al., 2008; NOVEMBRE et al., 2008).
Most of the results are rather obvious and explicable.
Several Middle Eastern populations are known to have Sub-Saharan African admixture, and this is shows up in the results.
Others may be more confusing because of the obscurity of the populations, but the Burusho clearly have ancient East Asian ancestry on clustering algorithms, so their presence is not surprising to me.
Similarly, the Russians in the HGDP data set have an ‘eastern’ affinity (or at least some do), either due to Finno-Ugric or Turkic ancestry (Tatars regularly assimilated into a Russian ethnic identity as the Tsars expanded their domains).
In short, admixture between two very distinct populations has the concrete result of producing striking genomic correlations.
Over time these correlations dissipate due to recombination.
The magnitude of dissipation can allow one to gauge the time in the past when the original admixture occurred. To the left is a section of a table which illustrates the most significant 3-population test scores in the HGDP.
The authors checked all the various combinations, and these came out at the top as likely admixtures (i.e., the two sources produce particular patterns in the target).
I will review the technical points in more detail in future posts, more for my own edification than yours. Four of the tests use comparisons of allele frequencies along explicit phylogenetic trees.
That’s so general as to be uninformative as a description, but I think it’s accurate to the best of my knowledge.
West Eurasian admixture into these groups is not unexpected.