 Their long occupation, initially in varying forms of isolation as hunter-gatherers, has made the region highly diverse, second only to Africa in human genetic diversity.Settled life emerged on the subcontinent in the western margins of the Indus river basin 9,000 years ago, evolving gradually into the Indus Valley Civilisation of the third millennium BCE.By 1200 BCE, an archaic form of Sanskrit, an Indo-European language, had diffused into India from the northwest, unfolding as the language of the "Rigveda", and recording the dawning of Hinduism in India.