Friday, January 11, 2019

Is there a gene for celibacy?

We see study after study of genes 'for' behavioral traits considered to be driven by selection: intelligence, athletic ability, criminality, recklessness, drug abuse, aggression, even being a caring grandmother. The list goes on and on and on. Simplistically stated, the idea is that behavioral traits have a genetic basis, usually a simple 'genetic' one, and that during human evolution, those genetically bestowed with the 'best' version of the trait outcompeted those unlucky enough to be less intelligent, less of a risk taker, a more fearful warrior, and so on.  That is pure Darwinian determinism: the bearers of the 'optimal' version of a trait systematically had more offspring, and thus the gene(s) for that version were selected for, and therefore increased in frequency.

This is why, for example, the basis of homosexuality is so curious to evolutionary biologists.  How could a behavioral trait that means its bearer does not have offspring ever have evolved?  How could a gene persist if it codes for something that interferes with reproduction so the gene isn't passed on? The most common explanation for this is that during the long millennia of human evolution, homosexuals mated and reproduced anyway, because homosexuality was culturally proscribed in the small groups in which humans lived.  Maybe that's so, but it's certainly no longer true in many cultures where being gay doesn't have to be hidden anymore, so should we now expect the frequency of homosexuality to fall? Another post hoc account is that homosexuals helped care for their relatives' children, enhancing their extended kinship and hence consistent with natural selection--a technically plausible but basically forced speculative explanation by those who want Darwinian determinism to be as universal as gravity.

In any case, the "cause" of homosexuality is certainly an interesting evolutionary puzzle, if it's assumed to be genetic.  It may well not be, of course -- perhaps sexual orientation is influenced by environmental exposures in utero or in infancy.  But, let's go with the genetic assumption.  Let's even assume that looking for genes for IQ, aggression and so many other behaviors is reasonable, because all these traits, as all traits, must be here because of natural selection.

In that case, it's very curious that there are so many traits that defy Darwinian explanation whose genetic basis isn't being explored. Where are the searches for genes for, say, voluntary celibacy, or use of birth control and non-celibates choosing not to have children, or for suicide, or child-beating, or infanticide, or abortion, or young men volunteering to be soldiers?  These are all traits that make no evolutionary sense and shouldn't have evolved, if such traits have a genetic basis.  We should be just as perplexed by the evolutionary history of these behaviors as we are by homosexuality. Why aren't we looking for genetic explanations?

I think it's a reflection of cultural values. It's rather akin to environmental epidemiologists never looking for the harmful effects of cauliflower, broccoli or Brussel's sprouts -- instead it's the things we like, our indulgences; alcohol, fatty foods, sugar, which reflect our Puritan scorn for pleasure.  I think we notice and think about what seem to us to be unacceptable aberrations, and give much less thought to what seems normal.  It's ordinary to us that nuns and priests choose not to reproduce, even if that is completely non-Darwinian, or that suicide bombers are generally of reproductive age and are foregoing having children.  Abortion may not be personally acceptable to you, but it's a societal norm.  Indeed, artificial birth control itself is highly problematic in a Darwinian world -- even worse for Darwinian theory, it sends women into the work force, away from their children.

Apparently we don't generally notice that these 'normal' behaviors are non-Darwinian -- our primary drive, consciously or unconsciously, but inherently, is supposed to be to perpetuate our genes.  If behaviors are genetically driven, selected for, then it's not just homosexuality -- which, until recently, was not socially acceptable -- that doesn't make evolutionary sense, it's any behavior whose primary ramification is not to send our genes into the next generation.

So, don't we have the same issue with explaining the evolutionary origin of all these behaviors as we do explaining homosexuality?  Perhaps.  But let's consider an explanation that's not generally proffered: Perhaps this is all just statistical 'noise' around a weak rather than precisely or strongly deterministic natural selection, that Nature is just sloppier than the strictly Darwinian view would expect.  The success of no species requires that every individual reproduce, so long as enough do. Culture is a powerful force -- once we respond to cultural dictates and norms, the simple evolutionary explanation of selection for optimal (in fitness terms) traits is much less convincing.  And, perhaps we didn't evolve to reproduce, just to have orgasms.

And, is there a gene for being dogmatic?

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