According to the speaker, given any two human beings picked at random, their genomes differ by about 3 million nucleotides (out of about 3 billion in all). About 25% of all known genes are polymorphic (occur in different forms in different people), and a typical person has different forms from their mother and father for about 10% of their genes. We were shown lots of tables of numbers gathered from studies of gene frequency in different populations. The overall point of all these tables was to demonstrate that about 85% of genetic variation occurs within geographically local groups, and only 15% between geographically separated groups. That is to say, for example, that two Korean people picked at random are likely to be nearly as genetically different as a Korean person and a French person. This contradicts the intuition that people who are so physically different are genetically far apart. The conclusion was that there is no evidence that race is a sensible biological concept for humans.
The speaker suggested a possible guess that might explain why visible differences are so prominent and yet so genetically insignificant: perhaps it's a result of sexual selection. He called into question traditional arguments for the evolution of skin pigmentation and pointed out that, while most people generally believe that the first humans developed in Africa and spread to other continents, those first humans did not necessarily look anything like Africans do today. Maybe people just got to be so dark-skinned or light-skinned because it became a locally attractive feature to have (just as the positive feedback loop of attractiveness led to the extreme displays of peacocks).
I especially thought that attending this lecture would be interesting and pertinent since i had just acquired and started reading The Bell Curve, a tremendously controversial book. Many people have called the book racist or pseudoscientific; i thought i would actually try reading it to see what was inside. The APA has a pair of contrasting reviews of the book, and Google offers lots of critiques and opinions. I've only just started reading it, but i'll try to give a report when i'm done. Has anyone else read the book?