Population genetics have revolutionized human anthropology, with differences in the DNA sequences between existing populations allowing for the retracing of human migration over time. In a new population genetics study published in Genome Biology, the labs of Lynn B Jorde and Fuli Yu present evidence for an ancient northern migration route out of Africa taken by the common ancestors of Eurasians, from whom today's East Asians, Europeans and Indians are descended. Their data also support a "delayed expansion" hypothesis for the history of Eurasians.

By sequencing a small part of the genomes of 92 individuals from four Indian population groups, and comparing the results with existing sequences of other populations from the HapMap project, Indian populations were shown to be highly genetically diverse. Surprisingly, in some cases Indian populations were found to be nearly as diverse as African populations.

Analyses of the sequences suggested that the Eurasian ancestors separated from African populations approximately 90 – 110,000 years ago but that the next expansion into separate population groups (East Asians, Europeans and Indians) was delayed, not occurring for another 40,000 years. The analyses also suggested that the Indian populations included in the study (Brahmin, Yadava and Mala/Madiga castes and the Irula tribe) had migrated to India via a northern route.

The findings from this study, in particular the high degree of genetic diversity and the discovery of a large number of new genetic variants, highlight the need for including multiple Indian populations in any wider discovery effort relating to the demographic history of the human Eurasian expansion.