These ideas are 'dangerous' in that it is perceived that any scientific conclusion about inherent differences, no matter how verifiable and unbiased, will lead to dangerous societal attitudes and prejudice. Dr. Sperber above mentions that "even if some natural inequality were established, it would not come near justifying any inequality in rights"--although it is obvious that this is exactly what the PC elements of society most fear (probably correctly...)
(It is ironic that the logic that says certain 'truths' are too dangerous for mankind because of how people might react to them applies to racial and gender differences, but not to religious differences. What if certain scientific discoveries happened to, say, undercut one's belief in the Bible, leading people to a life of sin and separation from God and salvation. Couldn't that be considered a more 'dangerous' side-effect than mere racism or sexism? And yet--surprise, surprise--science considers that a triumph instead of a tragedy...)
In his article, Kevin argues, "It's doubtful that anyone could actually prove there are significant genetic differences between the races, but the point is no one tries, since racial research is decidedly un-PC." However, Charles Murray and Richard Herrnstein argued exactly that in their book The Bell Curve. I quoted several excerpts from an article by Murray in an earlier post. Among those quotes was this one:
Several analyses have confirmed the genetic reality of group identities going under the label of race or ethnicity. In the most recent, published this year, all but five of the 3,636 subjects fell into the cluster of genetic markers corresponding to their self-identified ethnic group. When a statistical procedure, blind to physical characteristics and working exclusively with genetic information, classifies 99.9% of the individuals in a large sample in the same way they classify themselves, it is hard to argue that race is imaginary.
I think that the important thing to remember about such studies is that they only study averages and tendencies and say nothing about any one individual. Even if Blacks tend to be better athletes, it doesn't mean that a particular Black will be a better athlete than a particular White. For this reason, it is vital that we not put in place discriminatory policies, such as preventing Whites from trying out for school athletic teams.