Kluge: The Haphazard Construction of the Human Mind (Houghton Mifflin; 2008)

The standard tack in evolutionary psychiatry, the branch of evolutionary psychology that deals with mental disorders, is to explain particular disorders (or occasionally symptoms) in terms of hidden benefits.* We saw one example in the first chapter, the somewhat dubious suggestion that schizophrenia might have been selected for by natural selection because of a purported benefit that visions conveyed to tribal shamans, but there are many others. Agoraphobia has been viewed as a "potentially adaptive consequence of repeated panic attacks," and anxiety has been interpreted as a way of "altering our thinking, behavior, and physiology in advantageous ways." Depression, meanwhile, allegedly evolved as a way of allowing individuals to "accept defeat... and accommodate to what would otherwise be unacceptable low social rank."

If you're like me, you won't find these examples particularly compelling. Were schizophrenics really more likely than other people to become shamans? Were those who became shamans more successful than their non-schizophrenic counterparts in producing viable offspring? Even if they were, are shamans prevalent enough in history to explain why at least 1 in every 100 humans suffers from the disorder? The depression theory initially seems more promising; as the au

*Another strand of evolutionary psychology emphasizes the extent to which current environments differ from those of our ancestors. As Kurt Vonnegut Ir. (who before he became a novelist studied anthropology) put it, "It's obvious through the human experience that extended families and tribes are terribly important. We can do without an extended family as human beings about as easily as we do without vitamins or essential minerals." "Human beings will be happier," he wrote, "not when they cure cancer or get to Mars or eliminate racial prejudice or flush Lake Erie, but when they find ways to inhabit primitive communities again." I have great sympathy with this notion, but the stress of modern life is only a part of the story; as far as we can tell, mental disorders have been around for as long as humans have. Like virtually every aspect of mental life, mental illness depends on a mix of factors, some environmental, some biological.

thors note, it might well be better for the low man on the totem pole to accede to the wishes of an alpha male than to fight a battle that can't be won. Furthermore, depression often does stem from people's sense that their status is lower, relative to some peer group. But does the rest of the social competition theory even fit the facts? Depression isn't usually about accepting defeat, it's about not accepting it. A friend of mine, we'll call him T., has been clinically depressed for years. He's not particularly low in social rank (he's actually a man of considerable accomplishment). Yet although there is nothing objectively wrong with his life, he doesn't accept it: he ruminates on it. Depression hasn't mobilized him to improve his life, nor to keep him out of trouble; instead, it's paralyzed him, and it's difficult to see how paralysis could be adaptive.

Of course, I don't mean to suggest that one dubious theory is enough to rule out an entire line of work; certainly some physical disorders convey benefits, and there may well be analogous cases of mental disorders. The classic example of a physical disorder with a clear corresponding benefit is the gene that is associated with sickle cell anemia. Having two copies of the gene is harmful, but having a single copy of the gene alongside a normal copy can significantly reduce one's chance of contracting malaria. In environments where malaria has been widespread (such as sub-Saharan Africa), the benefits outweigh the potential costs. And, accordingly, copies of such genes are far more widespread among people whose ancestors lived in parts of the world where malaria was prevalent.