Mix and then match. Ancient Indians from the north (ANI) and south (ASI) of India first intermarried widely and then began sticking to their own groups.
“In India we celebrate the commonality of major differences,” wrote the celebrated author Shashi Tharoor about his native country. “We are a land of belonging rather than of blood.” Indeed, India’s 1.24-billion-strong population is one of the world’s most diverse, with 700 ethnic and language groups and possibly many more, depending on how they are counted. Today, most of these groups keep pretty much to themselves, only rarely marrying outsiders. But a new study concludes that several thousand years ago, the entire subcontinent underwent a period of massive intermarriage, shuffling its population’s genetic deck so thoroughly that it left clear traces—even in the genomes of today’s most isolated tribes.
In recent years, genetic studies of modern Indians have provided a host of new insights into the ancient history of this sprawling nation, which harbors nearly one-sixth of the world’s population. A key finding, reported in 2009 by a team led by geneticist David Reich of Harvard Medical School in Boston, was that most Indians today are descendants of two major population groups: Ancestral North Indians (ANI), who probably migrated into the subcontinent 8000 or more years ago from the Middle East, Central Asia, and Europe; and Ancestral South Indians (ASI), who were native to the region and had been there much longer. The study also showed that these two groups began to mix at some point in the past, although just when was not clear.