2009 September 24; 461(7263): 489–494 | David Reich, Kumarasamy Thangaraj, Nick Patterson, Alkes L. Price, and Lalji Singh
This study provides strong evidence for the existence of two ancient populations, the "Ancestral North Indians" (ANI) and the "Ancestral South Indians" (ASI), which are ancestral to most Indians today. The ANI is genetically close to Middle Easterners, Central Asians, and Europeans, while the ASI is distinct from both ANI and East Asians. The authors introduce methods to estimate ancestry without accurate ancestral populations, showing that ANI ancestry ranges from 39-71% in India, with higher levels in traditionally upper caste and Indo-European speaking groups. Groups with only ASI ancestry may no longer exist in mainland India, but the Andamanese are an ASI-related group without ANI ancestry, indicating that the peopling of the islands occurred before ANI-ASI gene flow on the mainland. Allele frequency differences between Indian groups are larger than in Europe, reflecting strong founder effects that have been maintained for thousands of years due to endogamy. These findings suggest that there will be an excess of recessive diseases in India, which should be screened and mapped genetically. The study also highlights the importance of understanding the history of population mixture in India to address medical implications and prioritize research on recessive diseases.This study provides strong evidence for the existence of two ancient populations, the "Ancestral North Indians" (ANI) and the "Ancestral South Indians" (ASI), which are ancestral to most Indians today. The ANI is genetically close to Middle Easterners, Central Asians, and Europeans, while the ASI is distinct from both ANI and East Asians. The authors introduce methods to estimate ancestry without accurate ancestral populations, showing that ANI ancestry ranges from 39-71% in India, with higher levels in traditionally upper caste and Indo-European speaking groups. Groups with only ASI ancestry may no longer exist in mainland India, but the Andamanese are an ASI-related group without ANI ancestry, indicating that the peopling of the islands occurred before ANI-ASI gene flow on the mainland. Allele frequency differences between Indian groups are larger than in Europe, reflecting strong founder effects that have been maintained for thousands of years due to endogamy. These findings suggest that there will be an excess of recessive diseases in India, which should be screened and mapped genetically. The study also highlights the importance of understanding the history of population mixture in India to address medical implications and prioritize research on recessive diseases.