Ancient roots for India’s rich diversity

Analysis of genetic variation in 132 individuals from 25 diverse groups in India reveals that two ancient, genetically divergent populations are ancestral to most Indians today. One lineage, termed Ancestral North Indian, is genetically close to Middle Easterners, Central Asians and Europeans. The other, Ancestral South Indian, is not close to any group outside the subcontinent. The answers to several long-standing questions emerge from this work. It seems that ‘caste’ has been a powerful force shaping marriage in India for thousands of years — some anthropologists argued that its current strength was a product of British colonialism. And the enigmatic ‘Negritos’ of the Andaman Islands are identified as an ancient isolate from the Ancestral South Indian population. Allele frequency differences between population groups are high, in part due to the custom of within-group marriages, so it is likely that there is an excess of recessive diseases in India that can be screened for and mapped genetically.