Tag Archives: date

ANI-ASI Admixture Dating

Posted by on June 25, 2012 169 comments

Similar to an earlier conference poster, Reich Lab's Priya Moorjani et al have another poster at SMBE. Here's the abstract:

Estimating a date of mixture of ancestral South Asian populations
Linguistic and genetic studies have demonstrated that almost all groups in South Asia today descend from a mixture of two highly divergent populations: Ancestral North Indians (ANI) related to Central Asians, Middle Easterners and Europeans, and Ancestral South Indians (ASI) not related to any populations outside the Indian subcontinent. ANI and ASI have been estimated to have diverged from a common ancestor as much as 60,000 years ago, but the date of the ANI-ASI mixture is unknown. Here we analyze data from about 60 South Asian groups to estimate that major ANI-ASI mixture occurred 1,200-4,000 years ago. Some mixture may also be older--beyond the time we can query using admixture linkage disequilibrium--since it is universal throughout the subcontinent: present in every group speaking Indo-European or Dravidian languages, in all caste levels, and in primitive tribes. After the ANI-ASI mixture that occurred within the last four thousand years, a cultural shift led to widespread endogamy, decreasing the rate of additional mixture.

I bolded the portion which seems new compared to the previous abstract.

ANI/ASI Admixture Dating

Posted by on September 1, 2011 38 comments

Via Razib, here's an interesting abstract from the International Congress of Human Genetics by David Reich's group:

Estimating a date of mixture of ancestral South Asian populations.

Linguistic and genetic studies have shown that most Indian groups have ancestry from two genetically divergent populations, Ancestral North Indians (ANI) and Ancestral South Indians (ASI). However, the date of mixture still remains unknown. We analyze genome-wide data from about 60 South Asian groups using a newly developed method that utilizes information related to admixture linkage disequilibrium to estimate mixture dates. Our analyses suggest that major ANI-ASI mixture occurred in the ancestors of both northern and southern Indians 1,200-3,500 years ago, overlapping the time when Indo-European languages first began to be spoken in the subcontinent. These results suggest that this formative period of Indian history was accompanied by mixtures between two highly diverged populations, although our results do not rule other, older ANI-ASI admixture events. A cultural shift subsequently led to widespread endogamy, which decreased the rate of additional population mixtures.

I would be very interested in reading that paper. Also, I wonder how many new samples did they genotype beyond the ones in Reich et al' Reconstructing Indian Population History and if I could get my hands on the new data.

I have a feeling that ANI (Ancestral North Indian) captures a bunch of different migrations and conquests etc, so I am not sure if it can be equated to Indo-European language movement.

I wonder if I can use HAPMIX or StepPCO to get similar admixture dating.