I would like to add a few things. I can trace my ancestors' origins back to the Indus Valley Civilization, which was located in the area which is now known as modern day Pakistan and the state of Gujarat. It was located near the Indus river. It was at some point in time that a community of 1000 Audichya Sahastra Brahmins migrated to Gujarat. I know that my parents descended from that community.
The Indus Valley Civilization, or the Harappan Civilization, is believed to have existed from around 3300 BCE to 1300 BCE. It was a tecnologically advanced civilization with metropolitan cities like Mohenjo-Daro, its own system of mathematics, its own writing system, knowledge of engineering, and its own religion. It's really amazing to be able to trace your ancestry back to an ancient civilization.