Diamond was very aware of the minefield he was stepping into and the only way he could talk about what he wanted to talk about was to dismiss out of hand any connection between race and intelligence.
The problem is, despite multidisciplinary squabbling about the definitions of race and intelligence (see above), and near universal distain for IQ tests, the puzzling fact that no one has been able to convincingly explain away the significant degree of variation seen in the U.S.
Is there a real difference?
Is it the tests?
Or are the differences entirely ones of culture, and environment?
Reminds me of the arguments about the dominance of Kenyans in distance events, no?
Clearly, the least plausible argument is to entirely blame the tests.
The most satisfying would be to proclaim at least some measurable difference.
The truth is most likely a combination of all three and Diamond's out of hand dismissal, not that I blame him for it (anything else would have been career suicide) makes his book reek that particular stench of academia.