The best of all possible forms

I have a longstanding argument with a number of very close friends, as well as with my sister, over the extent to which the myriad components of the human body, and human “traits,” have actually been selected. My friends, and my sister, argue that “if we’ve got it, it has a purpose”—meaning, at some point in our evolutionary journey, it was adaptive; it gave us an advantage in the whole game of survival and reproductive fitness. They vehemently dispute the idea that some traits may simply hitchhike along with other, specifically desirable ones, making them neither adaptive, nor maladaptive, but “spandrels” (incidental products of evolution that have no function).

Well, of course, natural selection does not really work at the level of the gene; it works at the level of the organism. Dalmations, bred for appearance and stamina, often suffer from genetic deafness—a trait that came along with the specifically selected traits. My friends argue, not without reason, that under more natural conditions (presumably in the wild), deafness would be so maladaptive as to be selected out. Okay, fair enough.

Here’s where we really part company. My friends and sis (henceforth referred to as "they") believe that, after all those years of evolution, the human body/form is pretty much perfectly adapted to its environment, by which they mean “the African savannah.” One friend even follows a “Paleolithic diet,” eating only those things that would have been available on the savannah (i.e., no grains other than rice, no dairy unless raw, no legumes). They argue that long life and great health will follow from adjusting our diet and lifestyle to best mimic the conditions for which we are so adapted.

Here’s my problem with all this:

1. Natural selection does not care about perfect health and long life. You only have to live long enough to reproduce; the more surviving offspring you have, the more your traits/genes get passed on. Biggest causes of death now—heart disease, cancer—figure well after the game of reproduction has been fought (and won or lost). (Disclaimer: Some people argue for the Grandma hypothesis--that organisms with “grandma” caregivers are more likely to survive to reproduce, making longevity, in a roundabout way, adaptive. I’m on the fence with this…)

2. There is no such thing as perfectly adapted; evolution is a compromise. A peacock’s tail makes him more attractive to mates, but more visible to predators. It’s always a tradeoff.

And my biggest problem with this is:

3. Natural selection does not really mean survival of the fittest. It means elimination of the unfittest. We like to think of nature as “red in tooth and claw,” where only the truly magnificent specimens can survive and pass on their genes, but for most periods of human (and early human) history and prehistory, conditions were not so dire. In any given generation, the norm is that only the very worst will not survive to reproduce. So to make it in the game of evolution, you only have to Not Suck. Thus, we do not have the best of all possible forms; we just don’t suck. We have fallen arches and lower back problems because the benefits of being bipedal outweigh the costs (benefit: it leaves our hands free; cost: fallen arches and lower back problems).

It’s interesting; I think for Enlightenment thinkers, this notion of the perfectability of the human form was the consolation prize for giving up on a notion of god. Maybe this wasn’t the best of all possible worlds. Evil was real. Nature was the mover and the shaker, not a benevolent creator god, and nature was a cruel and indifferent master/mistress. But, that very cruelty--the harshness of existence and the improbability of survival--ensured that humans were honed, over millenia, to something close to perfection. But it just ain't so. Oh, well; so much for consolation.