Dear Cecil: Are human beings still evolving? Or are we devolving? Are our genes, when passed on to our kids, copied faithfully like a digital recording? Or is the process more like a photocopy of a photocopy, deteriorating more and more with each generation? I hope it’s not the latter, because if the results are anything like those from the self-serve copy place down the street, we’re in big trouble. David Westwood, Santa Monica, California
David, it’s obvious you not only slept through Intro to Biology, you were a little groggy during a couple key college bull sessions, too. We covered this topic a little after 2 AM the second month of freshman year. The prevailing view was that humans weren’t evolving, because what with the welfare state and the miracle of modern medicine and all, natural selection (i.e., survival of the fittest) had ceased to operate.
Nonsense, I argued (correctly, of course, because even then I could see I was never wrong) — natural selection by definition is always at work. If nobody dies before reaching reproductive age, well, that merely meant that everybody got naturally selected.
You don’t get it, said my opponents. If there aren’t any differences in mortality among genotypes (isn’t it great the way I sling these words around like you know what I’m talking about?), that means the gene pool is static and we aren’t evolving.
Sure we are, sez I. The fundamental question isn’t whether people die young, it’s whether they fail to reproduce, or reproduce less abundantly than others. On this basis we can say that the genes for the following physical types or traits are slowly disappearing from the population:
(1) People so lacking in sex appeal that nobody could stand to get close enough for long enough to beget children with them. We may thus anticipate that in the distant future people will be extremely good looking and sociable, but nobody will know how to operate the computers.
(2) Yuppieness, since yuppies typically have fewer children later than other population groups. The people of the future, in all likelihood, will drink Bud, eat jalapenos, and believe that Cleopatra was … well, let’s not get into it. But you won’t have your parking space stolen by some sphincter in a Beamer, either.
(3) Certain other well known spiritual and physical callings, shall we say. You know who you are.
OK, so maybe Cecil is kidding around a little. We can’t assume any of the alleged traits above have a genetic basis. What’s more, widespread interbreeding among population groups has a leveling effect. You generally only see noticeable changes when a group is reproductively isolated and key genes get passed around by inbreeding, as with sickle-cell anemia in blacks and Tay-Sachs disease in Jews. But you get the idea: as long as some folks reproduce more than others for reasons related however tenuously to their genes, the gene pool isn’t completely static.
As for whether our genes are accurately reproduced, you silly goose, the genes always accurately reproduce. Except sometimes. On the latter occasions one of several things results: one, monsters — that is, grossly malformed babies resulting from a genetic mistake. Years ago most monsters died, but now many can be saved. This has made possible the National Football League. Two, useful mutations increasing one’s chances of reproductive success. Think of the first little mutant to discover he could comb his hair in a ducktail. Or, to bring up a more sober possibility, the first to become resistant to AIDS. Three, maladaptive but not immediately fatal mutations, such as those causing certain diseases.
So yes, we’re still evolving. But not very quickly. Most students of the subject say we haven’t changed much in the past 30-50,000 years, except that we’re now willing to eat head cheese. As for that sci-fi stuff about evolving giant brains … well, modesty prevents me from saying much about it. But it sure does make it a bitch to buy hats.
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