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Friday, March 2, 2012

ADMIXTURE analysis of West Eurasia - K=12 run

Moving up to K=12 (twelve ancestral clusters assumed) has resulted in a major shake up of the West Eurasian components. The Western European cluster from the K=11 run has been replaced by North Atlantic and Mediterranean clusters. Interestingly, the new North Atlantic has also eaten up a lot of the putative West Central Asian influence in samples from Northwestern Europe, basically changing the implied direction of gene flow, from east to west to west to east.

What this clearly shows is that it's not a good idea to take the results of a single ADMIXTURE run too literally. It's more appropriate to consider output from a variety of K when formulating theories, and then to cross check this info with results from other analyses using very different algorithms. Anyway, my impression here is that ADMIXTURE is now beginning to struggle with the lack of differentiation between the West Eurasian clusters, and producing quirkier results as well as more noise. I expect that the K=13 run will be an uphill battle, and most likely result in a fairly uninformative cluster somewhere. Hopefully I'll be proved wrong.

Key: Red = East Asian, Orange = Mediterranean, Yellow = Sub-Saharan, Light Green = South Asian, Green = North Asian, Aqua Green = East African, Aqua Blue = Caucasus, Light Blue = North Atlantic, Dark Blue = West Central Asian, Dark Purple = Southwest Asian, Light Purple = Baltic, Dark Pink = Southeast Asian. See spreadsheet for details. An image of the Fst (genetic distances) between the clusters can be found here.