posted on Nov, 28 2003 @ 11:53 AM
an interesting article-
"The "Weak Garden of Eden" model for the origin and dispersal of modern humans posits a spread around 100,000 years ago followed by population
bottlenecks. Then around 50,000 years ago a dramatic growth occurred in genetically isolated, small population. In a 1998 article Stanley Ambrose
proposed an alternative hypothesis, a volcanic winter scenario, to explain recent human differenciation. The bottleneck was caused by a volcanic
winter resulting from the super-eruption of Toba in Sumatra. If Ambrose's hypothesis is correct modern human races differentiated abruptly through
founder effect, genetic drift and adaptation to local environments around 70,000 years ago. "