“The problem with IQ tests is that they do produce group differences, and that’s unbelievably complicated and horrible. It’s complicated because it isn’t obvious how you should group people, if you’re going to do group analysis of IQ. For example, there’s more genetic diversity among Africans than there is among all the other human populations. So exactly how you put people in the bin of black, caucasian, and asian, let’s say—which are generally regarded as the three major racial groups—is far from obvious. That’s a basic scientific conundrum that’s right at the bottom of the IQ problem. But if you use the typical groupings, you do get ethnic differences. That starts to become extremely problematic, because the question, then, is 'why?' The answer to that is, 'we don’t know.'”