This week, the evolutionary biologist Michael Lynch has published a provocative paper (to mark his inauguration into the National Academy of Sciences) in which he makes another kind of forecast. Our future evolution, he warns, is going to lead to a devastating decline in our health. . .
Lynch concludes that every gamete (a sperm or egg) acquires the following:
–38 base-substitution mutations (a single “letter” of DNA changes to another one).
–3 small insertions or deletions of a stretch of DNA
–1 splicing mutation (which changes the combination of segments of a gene that cells use to build proteins)
–Plus some assorted other mutations (gene duplications, insertions of DNA copied by transposable elements, and so on).
All told, Lynch estimates a total of 50 to 100 mutations.
A lot of the new mutations in every new baby are harmless. But each baby may acquire a few harmful ones. These mutations rarely cause a swift death. Instead, in their totality, they slice off a tiny fraction of the total offspring an entire population can produce. Lynch estimates that mutations to protein-coding DNA cause the fitness of a population to decline by 1%. That’s assuming natural selection does not favor other mutations over these harmful ones.
Lynch acknowledges that natural selection is still in effect in humans, particularly in places where people never see doctors, let alone get clean drinking water. But as the world’s standard of living goes up, he argues, more and more people are being shielded from natural selection’s most intense effects–and harmful mutations are piling up.
In a matter of a few centuries, Lynch predicts, industrialized societies may experience a huge increase in harmful genes–”with significant incapacitation at the morphological, physiological, and neurobiological levels,” he writes.
Ironically, though Lynch's theory sounds suspiciously like the protect-our-genes ranting of paleo- and neo-eugencists, it fatally undermines the eugenic argument by pointing out how useless such a program would be. You can't stop the inevitable micromutations Lynch points to above, but you can go out of your way to make sure you're doomed by minimizing natural selection and maximizing the concentration of mutated genes by limiting your gene pool.
Battling this decline won’t be easy, says Lynch. Rather than a few big mutations causing the trouble, the decline will be brought about by a vast number of mutations, each with a very small effect. The fantasies of selective breeding dreamed of by eugenicists aren’t just loathesome–they’re also useless. Instead, Lynch argues for something that would make the eugenicists crazy. “Ironically, the genetic future of mankind may reside predominantly in the gene pools of the least industrialized segments of society,” he writes.
In short, if you're single, you need to do your part to save the human race by getting some hot you-on-somebody-else action on across ethnic barriers. That's right! It's no longer your creepy fetish; it's the only way to save humanity. Do it now, for the future.
