"Most of our ancestry as humans has occurred in Africa, so people have been in Africa for far longer than they've been outside of Africa. So genes for hundreds of thousands of years were evolving, changing inside of Africa, and then just a tiny group of people — maybe no more than 150 people, or a small group — left East Africa en route to populating the rest of the world. At each stop, their genes changed to accommodate their environments and sometimes just by random chance. ... But what this means is that most of the genetic differences that have been built up in our history are all still in Africa. All of us outside of Africa are just tiny subsets of a tiny subset that left Africa. So if you got rid of everyone in the world outside of Africa you would lose a little, but you would preserve most of the genetic variation for all of humanity.
"... [For] a particular trait, you might find the most diversity within an African population, as opposed to comparing someone in an African population and someone in a European population. So you might find the fastest 10 runners and the slowest 10 runners. But nobody is looking for the slowest 10 runners."
This makes COMPLETE sense to me. Of course where you have the most genetic diversity will you get the highest opportunity for extreme of the human population on both ends of the spectrum, both the fastest and the slowest.
But the conversation should not stop there, shouldn't we see genetic variability in all areas? Curliest hair? Straightest? Bluest eyes? Lightest blue? And so on.
Even further, when you get into more significant traits, we should see these in extremes as well. Specifically, I'm thinking of intelligence. If we believe there is some genetic component to intelligence (which it appears there are), then just as we would expect to see the fastest and slowest runners in Africa due to the genetic diversity, we should expect to see people at the extremes on the predisposition to intelligence in Africa.
However, according to this (http://www.cp-africa.com/2012/05/27/list-of-african-nobel-prize-winners/), there have been only 5 Nobel prize winners from Africa in anything other than Literature or Peace. I'm sure much of the reason is that there are not as many facilities for African research and science, but this seems like it needs to be addressed immediately.
To be clear, this book and research indicates there should be RIGHT NOW a set of folks in Africa that are as genetically predisposed to intelligence as anyone who has ever lived. One could argue it is humanity's responsibility to find these folks. IMMEDIATELY.