Will Saletan in Slate has been discussing some dangerous ideas regarding intelligence and genetics. He argues in this piece that the evidence is now clear that intelligence is highly inherited and that there are racial differences in intelligence. Here's part of that argument:
How could genes cause an IQ advantage? The simplest pathway is head size. I thought head measurement had been discredited as Eurocentric pseudoscience. I was wrong. In fact, it's been bolstered by MRI. On average, Asian-American kids have bigger brains than white American kids, who in turn have bigger brains than black American kids. This is true even though the order of body size and weight runs in the other direction. The pattern holds true throughout the world and persists at death, as measured by brain weight.
According to twin studies, 50 percent to 90 percent of variation in head size and brain volume is genetic. And when it comes to IQ, size matters. The old science of head measurements found a 20 percent correlation of head size with IQ. The new science of MRI finds at least a 40 percent correlation of brain size with IQ. One analysis calculates that brain size could easily account for five points of the black-white IQ gap.
I know, it sounds crazy. But if you approach the data from other directions, you get the same results. The more black and white scores differ on a test, the more performance on that test correlates with head size and "g," a measure of the test's emphasis on general intelligence. You can debate the reality of g, but you can't debate the reality of head size. And when you compare black and white kids who score the same on IQ tests, their average difference in head circumference is zero.
But in a separate piece Saletan argues, "So what." Here he articulates why these findings about the 
genetic component of intelligence does not undermine liberalism's dedication to equality. To summarize Saletan's argument, despite genetic differences in intelligence, these are only generalizations. Individuals of any race may defy generalizations so we should judge people as individuals, not as members of groups. Second, even those who buy strong genetic influence on intelligence say that 40%-50% of intelligence in environmentally based. Thus how we raise children is as important as genetic predispositions. Next, intelligence is not a determiner of human worth. As Lincoln argued, even if there are physical (i.e., genetic) differences between white and Negro, that does not mean the Negro is not a man without rights derived from nature. Fourth, there are abilities beyond intelligence. For example, good judgment and intelligence do not always co-exist in individuals. These are two different abilities. This why, for example, George Washington was a better president than John Adams even though Adams probably had a higher I.Q. Lastly, and related to the environmental factors in intelligence, improvements in health and education can increase the intelligence of those various groups that might have generally lower intelligence.
Saletan has made a significant contribution. He has told us something we don't want to believe, and then given us the way to reason back to our best principles.
Update: Readers should take in this response to Saletan that is quite damning of Saletan's sourcing.
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