To be sure, symptoms vary among individuals, both in severity and in number. Just as no two colds are exactly alike, no two people diagnosed with a given mental illness experience it in precisely the same way. Some people with depression, for example, are dysfunctional, and some aren’t; some people with schizophrenia hear voices, and others don’t.
And diagnosis remains an inexact science. There are a few disorders (such as multiple personality syndrome) whose very existence is controversial, and a few “conditions” used to be labeled as disorders but never should have been (such as homosexuality, removed from the DSM-III in 1973).[50] But by and large, there is an astonishing amount of consistency in the ways in which the human mind can break down, and certain symptoms, such as dysphoria (sadness), anxiety, panic, paranoia, delusions, obsessions, and unchecked aggression, recur again and again.
When we see the same basic patterns over and over, there has to be a reason for them. What is the mind, such that it breaks down in the ways that it does?
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.[51] 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 authors 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.
But while some physical disorders do demonstrably bring about offsetting benefits, most probably don’t, and, with the possible exception of sociopathy,[52] I don’t think I’ve ever seen a case of mental illness offering advantages that might convincingly outweigh the costs. There are few, if any, concrete illustrations of offsetting advantages in mental illness, no mental sickle-cell anemia that demonstrably protects again “mental malaria.” Depression, for example, doesn’t ward off anxiety (in the way that a propensity for sickling protects from malaria) — it co-occurs with it. Most of the literature on the alleged virtues of mental disorders simply seems fanciful. All too often, I am reminded of Voltaire’s Dr. Pangloss, who found adaptive virtue in everything: “Observe, for instance, the nose is formed for spectacles, therefore we wear spectacles. The legs are visibly designed for stockings, accordingly we wear stockings. Stones were made to be hewn and to construct castles.”
It’s true that many disorders have at least some compensation, but the reasoning is often backward. The fact that some disorders have some redeeming features doesn’t mean that those features offset the costs, nor does it necessarily explain why those disorders evolved in the first place. What happy person would volunteer to take a hypothetical depressant — call it “anti-Prozac” or “inverse Zoloft” — in order to accrue the benefits that allegedly accompany depression?
At the very least, it seems plausible that some disorders (or symptoms) may appear not as direct adaptations, but simply from inadequate “design” or outright failure. Just as cars run out of gas, the brain can run out of (or run low on) neurotransmitters (or the molecules that traffic in them). We are born with coping mechanisms (or the capacity to acquire them), but nothing guarantees that those coping mechanisms will be all powerful or infallible. A bridge that can withstand winds of 100 miles per hour but not 200 doesn’t collapse in gusts of 200 miles per hour because it is adaptive to fail in such strong winds; it falls apart because it was built to a lesser specification. Similarly, other disorders, especially those that are extremely rare, may result from little more than “genetic noise,” random mutations that convey no advantage whatsoever.
Even if we set aside possibilities like sheer genetic noise, it is a fallacy to assume that if a mental illness persists in a population, it must convey an advantage. The bitter reality is that evolution doesn’t “care” about our inner lives, only results. So long as people with disorders reproduce at reasonably high rates, deleterious genetic variants can and do persist in the species, without regard to the fact that they leave their bearers in considerable emotional pain.[53]
All this has been discussed in the professional literature, but another possibility has gotten almost no attention: could it be that some aspects of mental illness persist not because of any specific advantage, but simply because evolution couldn’t readily build us in any other way?
Take, for example, anxiety. An evolutionary psychologist might tell you that anxiety is like pain: both exist to motivate their bearers into certain kinds of action. Maybe so, but does that mean that anxiety is an inevitable component of motivation, which we would expect to see in any well-functioning organism? Not at all — anxiety might have goaded some of our prelinguistic, pre-deliberative-reasoning ancestors into action, but that doesn’t make it the right system for creatures like us, who do have the capacity to reason. Instead, if we humans were built from the ground up, anxiety might have no place at alclass="underline" our higher-level reasoning capacities could handle planning by themselves. In a creature empowered to set and follow its own goals, it’s not clear that anxiety would serve any useful function.
50
In an earlier era, there was “the inability to achieve vaginal orgasm,” “childhood masturbation disorder,” and drapetomania, the inexplicable desire on the part of some slaves to run away, or what I like to think of as freedom sickness.
51
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.
52
Although sociopathy would be unlikely to spread through an entire population, it is not implausible that in a society in which
53
Evolution is also flagrantly unconcerned with the lives of those past child-bearing age; genes that predispose people to Huntington’s chorea or Alzheimer’s disease could bear some hidden benefit, but the disorder could persist even if it didn’t, simply because, as something that happens late in life, the bottom line of reproductive fitness isn’t affected.