To begin with, the author makes what I consider are uncontroversial claims:
- Human evolution has not stopped, and evolution can work rapidly over as few as 20-30 generations.
- Human evolution and civilization goes hand in hand. For instance, in a large scale urbanized civilization, violent criminals are heavily punished, leading to aggression being bred out of the gene pool in relatively short order. In other words, humans have domesticated themselves over time.
- There's a strong relationship between geography and the type of civilization that evolves.
The big stretch in this book is when he claims that as a result of the cultural forces at play, the Western nations therefore evolved stronger tendencies towards novelty seeking, while the Asians evolved stronger tendencies towards conformity. This sneakily promotes some fairly obvious stereotypes again, with very little evidence. We simply don't know enough about genetics at this point to understand how personality is molded, and which parts of personality is determined by the environment, and which parts are what you are born with.
Now, there are some other claims that I think are quite believable. For instance, why have there been a preponderance of Jews in the sciences and other intellectual fields? Why are so many major award winners (Nobel prizes, etch) Jewish? There's quite a bit of evidence that there's been quite severe selection in the Jewish gene pool for IQ, which has also come along with a number of disadvantages such as genetic diseases unique to that race. This is entirely believable, especially since some of the genes creating those genetic diseases have also been linked to higher IQ.
The net result is that while I think this book is worth reading, especially in his debunking of say, Guns Gems and Steel, some of its wilder claims are a bit hard to believe. I can certainly see some politically minded folks seizing on this book as an opportunity to advance their causes. I fully expect certain sections of this book to be debunked in later research. But I'd recommend this book for everyone to read, bearing all these caveats in mind.