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 on that solution. New systems evolve on top of older systems, even where starting from scratch might objectively make more sense.
Addictions to thrills, drugs, and alcohol result from an imperfect compromise between something very old (dating back hundreds of millions of years, long before humans existed) and something new (dating back no more than a few hundred thousand years, an eye blink in evolution).
What’s old is our reflexive systems. For most of human prehistory, short-term thinking was practically the only thing that mattered: Predator or prey? Fight or flee? Early hominids that made snap decisions like that effectively survived; those that didn’t perished.
Much newer is a different system, one that deliberates and reflects. The trouble is that reflexive systems, because they are older, tend to dominate. If we see a chocolate cake, we eat it, no matter what we might have said at New Year’s about dieting.
The paradox of drug and alcohol abuse is that addicts know that their lives are worse off in the long run. But in the immediacy of the moment, our reflexive systems—precisely because they are so much older—still hold the steering wheel. Maybe in the millennia to come, our deliberative systems will integrate better with our reflexive systems. Until then, balancing short-term pleasure with what makes the most sense in the long run will remain, for all of us, a constant struggle.