@Esedess – Not sure, but I read Bill Bryson’s book many years ago. The population bottleneck is a well-researched subject. Might be linked to the Toba eruption. There are a lot of Internet citations of Woodruff’s 55 chimps observation. Here’s an example:
http://cogweb.ucla.edu/ep/Paleoanthropology.html
“Woodruff and Gagneaux translated the variation in the DNA sequences within humans, chimpanzees, and gorillas into a measure of genetic diversity. Chimps and gorillas, they found, have roughly equal level of diversity. Humans, however, although we are spread out over a vastly larger geographic area, have a significantly lower level of genetic diversity. Woodruff sums it up succinctly: ‘There’s more diversity in one social group of 55 chimps than in the entire human population.’ This lack of genetic diversity suggests the human lineage has gone through a population bottleneck at some point in its past history.”
I love the quote because it makes racism even more ridiculous and stupid than it already is. There is no biological justification for the notion of human races.