My parents, looking east and west

Yesterday Michelle decided to put up a post with her own analysis of her ADMIXTURE results. With that in mind, I thought I’d revisit some results from my parents. After many runs of ADMIXTURE, both by myself and Zack, some consistent differences seem to crop up. To review, one of the big surprises from genotyping my parents is that both of them have about the same “East Asian” element of ancestry which is very distinctive from the conventional South Asian mix. Because both of my parents lack any oral history of recent admixture I posited that this element may be a uniform substrate common among eastern Bengalis, and that it was absorbed during the initial period of settlement and demographic expansion on the frontier in the period between 1000-1500 A.D. By analogy, low levels of Amerindian admixture persist across Brazilians, and African admixture among Mexicans, but because the admixture dates back several hundred years it does not seem to have percolated down to the present in oral history (though some old stock Brazilians of predominantly Portuguese origin have been able to infer Amerindian ancestry by looking at the church marriage records of their ancestors, and …