Razib Khan in Gene Expression:
There is a new paper out of the Reich lab, Genetic Evidence for Recent Population Mixture in India, which follows up on their seminal 2009 work, Reconstructing Indian Population History. I don’t have time right now to do justice to it, but as noted this morning in thepress, it is “carefully and cautiously crafted.” Since I am not associated with the study, I do not have to be cautious and careful, so I will be frank in terms of what I think these results imply (note that confidence on many assertions below are modest). Though less crazy in a bald-faced sense than another recent result which came out of the Reich lab, this paper is arguably more explosive because of its historical and social valence in the Indian subcontinent. There has been a trend over the past few years of scholars in the humanities engaging in deconstruction and intellectual archaeology which overturns old historical orthodoxies, understandings, and leaves the historiography of a particular topic of study in a chaotic mess. From where I stand the Reich lab and its confederates are doing the same, but instead of attacking the past with cunning verbal sophistry (I’m looking at you postcolonial“theorists”), they are taking a sledge-hammer of statistical genetics and ripping apart paradigms woven together by innumerable threads. I am not sure that they even understand the depths of the havoc they’re going to unleash, but all the argumentation in the world will not stand up to science in the end, we know that.
Since the paper is not open access, let me give you the abstract first:
Most Indian groups descend from a mixture of two genetically divergent populations: Ancestral North Indians (ANI) related to Central Asians, Middle Easterners, Caucasians, and Europeans; and Ancestral South Indians (ASI) not closely related to groups outside the subcontinent. The date of mixture is unknown but has implications for understanding Indian history. We report genome-wide data from 73 groups from the Indian subcontinent and analyze linkage disequilibrium to estimate ANI-ASI mixture dates ranging from about 1,900 to 4,200 years ago. In a subset of groups, 100% of the mixture is consistent with having occurred during this period. These results show that India experienced a demographic transformation several thousand years ago, from a region in which major population mixture was common to one in which mixture even between closely related groups became rare because of a shift to endogamy.
I want to highlight one aspect which is not in the abstract: the closest population to the “Ancestral North Indians”, those who contributed the West Eurasian component to modern Indian ancestry, seem to be Georgians and other Caucasians.Since Reconstructing Indian Population History many have suspected this. I want to highlight in particular two genomebloggers, Dienekes and Zack Ajmal, who’ve prefigured that particular result. But wait, there’s more!