Around 65,000 years ago, initial settlements began in Andamans & ancient south India Another 25,000 years later, the ancient north Indians emerged Eventually, north and south populations met, giving rise to a different set Present-day Indians are a mix of north and south, with genomic strains from two distinct ancestors—the Ancestral North Indian & Ancestral South Indian .
The Indian traditional habit of marrying within one’s caste or community leads to genetic mutations, thus explaining why certain diseases are concentrated only in a particular pocket of the population in India. The research paper that restructures the Indian population history carries important findings that have medical implications. That many modern groups of people in India have descended from a small number of people is what scientists technically describe as a “founder event’’—a rampant Indian practice of people marrying within small group of people. Senior scientist with Centre for Cellular and Molecular Biology (CCMB), Kumarasamy Thangaraj says that because of this “high endogamy’’ within the country, a practice that dates back to several thousand years, makes these pockets genetically unique. “Because of this, there may be mutation in the gene that leads to various diseases,’’ Thangaraj says. And thus recessive hereditary diseases (single gene disorders that occur when person carries two abnormal or malfunctioning copies of a disease causing gene) are seen among Indians who have descended from a small group of founders. Like thalassemia, wherein a couple (both carriers) carrying one abnormal and normal gene each pass on the abnormal ones to the child. Researchers say there is a certain genetic mutation seen specifically in the Indian sub-continent alone, which they have been able to connect with the cardiac condition. “The study gives us an understanding why the incidence of cardiac disease is different in the Indian sub-continent from the rest of the world,’’ says Thangaraj.