The impression I got was that there may have been only about 300,000 10,000 years ago
But the population suddenly surged to about 2 million a couple of thousand years ago.
It has been suggested the ice age had ended and with warmer conditions plants and animals reproduced faster and the native populations followed that trend.
The figure of about 2 million was quoted in my reference from memory, but I would have to find it from somewhere in the 1000+ pages of the book.
