Even sex has its puzzling side. That sex is enjoyable is perhaps no surprise: if sex weren't fun for our ancestors, we simply wouldn't be here. Sex is, after all, the royal road to conception, and without conception there would be no life. Without life, there would be no reproduction, and legions of 'selfish genes' would be out of work. It seems like a no-brainer that creatures that enjoy sex (or at least are driven toward it) will outpropagate those that do not.
But having a taste for sex is not the same as pursuing it nonstop, to the virtual exclusion of anything else. We all know stories of politicians, priests, and plain ordinary folk who destroyed their life in relentless pursuit of sex. Might a Martian question whether our contemporary need for sex is as miscalibrated as our need for sugar, salt, and fat?
The Martian would eventually come to realize that although the core notion of pleasure as motivator makes a good deal of sense, the pleasure system as a whole is a kluge, from top to bottom. If pleasure is supposed to guide us to meet the needs of our genes, why do we humans fritter away so much of our time in activities that don't advance those needs? Sure, some men may skydive to impress the ladies, but many of us ski, snowboard, or drive recklessly even when nobody else is watching. When such a large part of human activity does something that
And indeed there is, but it's not about minds that are optimal, but about minds that are clumsy. The first reason should, by now, seem familiar: the neural hardware that governs pleasure is, like much of the rest of the human mind, split in two: some of our pleasure (like, perhaps, the sense of accomplishment we get from a job well done) derives from the deliberative system, but most of it doesn't. Most pleasure springs from the ancestral reflexive system, which, as we have seen, is rather shortsighted, and the weighting between the two systems still favors the ancestral. Yes, I may get a slight sense of satisfaction if I waive my opportunity to eat that cr?me brl?e, but that satisfaction would almost certainly pale in comparison to the kick, however brief, that I would get from eating it.* My genes would be better off if I skipped dessert — my arteries might stay open that much longer, allowing me to gather more income and take better care of my future offspring — but those very genes, due to their lack of foresight, left me with a brain that lacks the wisdom to consistently outwit the animalistic parts of my brain, which are a holdover from an earlier era.
The second reason is more subtle: our pleasure center wasn't built for creatures as expert in culture and technology as we are; most of the mechanisms that give us pleasure are pretty crude, and in time, we've become experts at outwitting them. In an ideal world (at least from the perspective of our genes), the parts of our brain that decide which activities are pleasurable would be extremely fussy, responding only to things that are truly good for us. For example, fruits have sugar, and mammals need sugar, so it makes sense that we should
*My friend Brad, who hates to see me suffer abstemiously in the service of some abstract long-term good, likes to bring me to a restaurant called Blue Ribbon Sushi, where he invariably orders the green tea cr?me brl?e. Usually, despite my best intentions, we wind up ordering two.
have evolved a 'taste' for fruit; all well and good. But those sugar sensors can't tell the difference between a real fruit and a synthetic fruit that packages the flavor without the nutrition. We humans (collectively, if not as individuals) have figured out thousands of ways to
And watermelon-flavored candy is only the start. The vast majority of the mental mechanisms we use for detecting pleasure are equally crude, and thus easily hoodwinked. In general, our pleasure detectors tend to respond not just to some specific stimulus that might have been desirable in the environment of our ancestors, but to a whole array of other stimuli that may do little for our genes. The machinery for making us enjoy sex, for example, causes us to revel in the activity, just as any reasonable evolutionary psychologist would anticipate, but not just when sex might lead to offspring (the narrowest tuning one might imagine), or even to pair bonding, but much more broadly: at just about any time, under almost any circumstance, in twos and threes and solo, with people of the same sex and with people of the opposite sex, with orifices that contribute to reproduction and with other body parts that don't. Every time a person has sex without directly or indirectly furthering their reproductivity, some genes have been fooled.
The final irony, of course, is that even though sex is incredibly motivating, people often have it in ways that are deliberately designed
To be sure, evolutionary psychologists have tried to find adaptive value in at least one of these variations (homosexuality), but none of the explanations are particularly compelling. (There is, for example, the 'gay uncle' hypothesis, according to which homosexuality persists in the population because gay people often invest considerable resources in the offspring of their siblings.)* A more reasonable accounting, in my view, is that homosexuality is just like any other variation on sexuality, an instance of a pleasure system that was
The situation with sex is fairly typical. A substantial portion of our mental machinery seems to exist in order to assess reward (a proxy for pleasure), but virtually all of that machinery allows a broader range of options than might (from a gene's-eye view) be ideal. We see this with enjoyment of sugar — a hot fudge sundae just about always brings pleasure, whether we need the calories or not — but also with more modern compulsions, like addiction to the Internet. This compulsion presumably begins with an ancestral circuit that rewarded us for obtaining information. As the psychologist George Miller put it, we are all 'informavores,' and it's easy to see how ancestors who liked to gather facts might have outpropagated those who showed little interest in learning new things. But once
*The trouble is there's no evidence that all that good uncle-ing (for relatives that are only one-eighth genetically related) offsets the direct cost of failing to reproduce. Other popular adaptationist accounts of homosexuality include the Sneaky Male theory (favored by Richard Dawkins) and the Spare Uncle theory, by which an uncle who stays home from the hunt can fill in for a dad who doesn't make it home.
flf homosexuality is a sort of evolutionary byproduct, rather than a direct product of natural selection, does that make it wrong to be gay? Not at all; the morality of sexuality should depend on
again we have a system that hasn't been tuned precisely enough: it's one thing to get a kick from learning which herbs help cure open wounds, but another to get a kick from learning the latest on Angelina and Brad. We would probably all be better off if we were choosier about what information we sought, ? la Sherlock Holmes, who notoriously didn't even know that the earth revolved around the sun. His theory, which we could perhaps learn from, goes like this:
