Unity in Diversity: India’s Population Genetics

India is a conglomerate of multitude of languages, ethnicities, castes, tribes and religions. While language and ethnicity are geographical divisions, caste and religion are socio-cultural divisions. The origin and diversity of population of India has been the subject of speculation for long.

The major present day view is based on the ‘Aryan invasions hypotheses’, postulated during late 19th century, which suggest the migration of Aryans from west Asia or Europe to northern India. These hypotheses, based mainly on linguistic studies, suggest the arrival of Aryans towards the end of Indus valley civilization at about 1800 BCE. There are also opposing views, though not favorite, that the focus was India and migrated to the west.

Researchers from Center for Cellular and Molecular Biology in Hybrabad, India along with collaborators at Harvard University have published a population genetics study on Indian population this week in journal Nature (September 23, 2009). Population genetics is the study of allele frequency and changes under the influence of various evolutionary pressures. They analyzed thousands of DNA variations from the genome of 132 individuals belonging to many ethnic groups from India to come to their conclusions. They draw compelling evidence about 2 major founder populations which makes up most of the present day Indians, who are a mixture of these now. An Ancestral South Indian group, found only in India, and an Ancestral North Indian group distantly related to west Asian and European populations.

Does the current finding that the Ancestral North Indian founder population is related to west Asians support any of these hypotheses? Probably not, the Aryan invasion is estimated at about 1800 BC, while the age of Ancestral North Indian founder population is tens of thousands of years older. Like the present day Indians, the people at the time of Indus valley civilization may already have a mixed genetics of both North Indian and South Indian founder population. In fact, none of the recent genetics studies support an Aryan Genetics trait for this period.

Anthropogenesis, or study of human evolution, have put modern human to have evolved about 100,000 years ago. The ‘out of Africa’ hypothesis assume human to have originated in Africa and spread across the world. While an alternate multiregional hypothesis argue geographically distinct but interbreeding parallel evolution of humans. Is the Ancestral South Indian founder population, which probably much older than the Ancestral North Indian founder population, came from Africa or evolved in South Asia?

Some of the more recent genetics studies on mitochondrial DNA and Y chromosome variations also do not support an Aryan invasion theory. Genetic studies including more ethnic groups and larger population samples are needed to paint a better picture of human evolution and migration patterns in India and South Asia.