Byline: Gary Marcus
Why has evolution let drugs be fun?
When I was in a college, a slightly older friend, smart as a tack and admired by all, died from an overdose of nitrous oxide--a drug that recently popped up in the news when it was alleged to have played a role in Demi Moore's hospitalization. From an evolutionary standpoint, drug abuse is puzzling: Why should people find pleasure in the killing of their own brain cells? Why isn't the brain wired to reject any actions that would actively cause it harm?
In a perfect world, nature would have already programmed us to avoid self-destructive short-term thrills, and we would be perfectly rational actors, never taking needless risks. Dangerous activities like drug use and reckless driving highlight an important gap between what might seem on paper to be optimal for evolution and biological reality.
The dirty secret is that evolution isn't, in fact, perfect. It's just a random process. Over time, it generally produces good results, but there's no guarantee, because there is no intelligent designer overseeing the show. Instead, evolution sometimes alights upon rather clumsy solutions--what engineers call kluges--that get the job done. Think, for example, of the human spine, a single column that supports much of our body weight. If we had three columns arranged in tripodlike array, we'd have a lot less back pain. But evolution simply never hit …