It is hard to credit that Orr really believes that (a) showing that a trait is heritable is the same as knowing its cause, (b) explaining how an ability works is the same as explaining why it varies, and (c) the fitness of an individual does not depend on the composition of the population. But the phenomenon is anything but “esoteric,” “exotic,” or “baroque.” There are, of course, empirical controversies over whether it is the best explanation of particular phenomena, including psychopathy. Many biologists believe that in ecology and social evolution, frequency-dependent selection is the rule, not the exception. It has been invoked to explain the 50:50 sex ratio, host-parasite and pathogen–immune system co- evolution, blood types and other polymorphisms, and all the behavioral phenomena (aggression, territoriality, cooperation) analyzed by evolutionary game theory. But when it comes to the question of what makes people within the mainstream of a society different from one another …the nature-nurture debate, as it has been played out for millennia, really is over, or ought to be.įinally, Orr dismisses the hypothesis that psychopathy is a product of frequency-dependent selection, which he calls “an esoteric evolutionary phenomenon.” Frequency-dependent selection simply means that the fitness of an individual depends on the relative abundance of phenotypes in the population. The nature-nurture debate is, of course, far from over when it comes to identifying the endowment shared by all human beings and understanding how it allows us to learn….

The contradiction evaporates when one reads the full quotation: Similarly, “the idea that nature and nurture interact to shape some part of the mind might turn out to be wrong” but “the nature-nurture debate, as it has been played out for millennia, really is over, or ought to be.” Heritability is always partial, implying that other factors play a role, and it is consistent with many causes, including the wiring of the brain, tuning of the immune system, and release of prenatal hormones. In fact the two statements are consistent: to show that a trait is heritable is not to explain its cause. tells us early on, for instance, that there is good evidence that “sexual orientation” is heritable but later on that “no one knows why some boys become gay.”

Orr criticizes my avoidance of simplistic arguments as “talking out of both sides of his mouth” or invoking “exotic” evolutionary processes.

Orr is more reasoned than his predecessors, but still makes many misleading claims. Allen Orr’s review of The Blank Slate falls into a familiar genre: the all-out attack on books that connect biology to human affairs.

The blank slate pinker