Friday, July 12, 2013

Acid Tongues and Tranquil Dreamers

…The fact that, in general, only the best-adapted member of a species will survive to reproductive age.
        pg. 118, Acid Tongues and Tranquil Dreamers, Michael White

[Having no way to contact Mr. White, I thought I'd let this note free on the Internet. Go, little note, fly away.]

Dear Michael,

My son thoughtfully turned me onto your book and I’ve been thoroughly enjoying it. I do quibble about the style sheet used to inform your punctuation, but that’s a minor point.

A somewhat larger point is illustrated by the sentence reprinted above, the one about “best-adapted members,” which itself illustrates a common misunderstanding of Darwinian evolution. As written, the sentence implies that natural selection is done at the individual level, the same error the social Darwinists make (and, frankly, most people).

The reality is that individual survival has little or nothing to do with natural selection. In general, most members of a species survive until reproductive age as one mounts the evolutionary chain. Those species designed with massive infant-death rates—frogs, say—are designed with the scatter-shot effect in mind: those who survive do so because of sheer luck, the predator didn’t find them; one has enough offspring that who gets eaten is immaterial. By the time one gets to, say, zebras or people, most offspring are expected to survive.

Natural selection is done at the genomic level. What that says is that, on average, individuals who possess mutation X have a better reproductive rate than those who don’t possess it. It’s concerned about the overall average, not the success of any particular individual. For example, an individual might have a mutation which would allow the possessors, on average, a longer life span; but that individual might have only one offspring before being dispatched by misfortune. Nonetheless, thanks to that one offspring, the mutation could be spread throughout the species, even though it gave no benefit to the individual in whom the mutation occurred.

The confusion appears to be a conflation of pecking order and natural selection. It’s fairly understandable that, observing natural pecking orders, one thinks that the selecting done to achieve that order is the same selecting that determines the direction of evolutionary change or dominance. They are unrelated, but, unfortunately, most people equate the two, as the quoted sentence illustrates.

Pecking orders evolved, not to insure that the best genes get together, but rather to maintain order within the species. Not only did pecking orders evolve, so did infidelity, which insures that, despite pecking orders, the gene pool will continue to be thoroughly mixed. It’s the mixing which is important, not the dominance.

Thanks for your time,

Johan Mathiesen
Portland, OR

No comments:

Post a Comment