“From genetic data, remarkably, you see this picture emerging of cultural change,” Reich said. The population mixture didn’t happen in pockets—it was a profound mixing that has left traces in the DNA of people in all areas of India today. But that came to an abrupt halt around 2,000 years ago, likely due to the implementation of the caste system, Reich said.
Supporting evidence for the genetic interpretation comes from an unlikely source: the Rig Veda, an ancient text dating back to about 1500 B.C. Different portions of the text are thought to have been written at different times, and the most ancient ones do not include references to the caste system. Those mentions come in later versions.
Story: Carolyn Y. Johnson, Boston Globe | Photo: Wikimedia Commons