[JustDoItAlways]

Here are a few links to the population bottleneck studies. Not proved of course but it would be difficult to prove this kind of thing. The best proof is still in our DNA.

http://www.everything2.com/index.pl?node_id=1420924

http://www.andaman.org/book/app-r/ch5_bottleneck/textr5.htm

http://www.jqjacobs.net/anthro/paleo/bottleneck.html

http://www.human-evol.cam.ac.uk/Members/Students/jones.htm

http://www.bradshawfoundation.com/evolution/

[blam]

There was an explosion of human branches after the Toba eruption and a lesser one again after the Last Glacial Maximum(LGM). I believe it was the LGM that caused Mongoloids and Caucasian to be defined from a common source...and, IMO, that source was the Jomon - Ainu people who dominated most of Asia 18-21,000 years ago.