Isolated remains of Homo erectus in Hathnora in the Narmada Valley in central India indicate that India might have been inhabited since at least the Middle Pleistocene era, somewhere between 500,000 and 200,000 years ago. Tools crafted by proto-humans that have been dated back two million years have been discovered in the northwestern part of the subcontinent. The ancient history of the region includes some of South Asia's oldest settlements and some of its major civilisations. The earliest archaeological site in the subcontinent is the palaeolithic hominid site in the Soan River valley. Soanian sites are found in the Sivalik region across what are now India, Pakistan, and Nepal.