[Little Bill]

....population in 13,000BC was 8.5 million.

How did he come up with that number? The number seems to small to sustain genetic viablity, when you look at the area we are talking about.

[LostTribe]

If you are interested in ancient population numbers you might be interested in those cited HERE. They are arrived at by simply averaging the estimates from a variety of respectable publicly available sources.