Tuesday, June 05, 2007

Missing the point on evolution

GNXP pointed out a nice rant on Good Math, Bad Math about a silly new book that preaches against the theory of evolution.

Mark Chu-Carroll thoroughly tears into the book, knocking down its math and logic in detail. However, he passes up the best argument: even if all the other B.S. were correct, a species' parasites and prey bulldoze its fitness peaks into fitness craters with overlapping rings. The more strongly mutations are rewarded and punished, the smoother the landscape becomes and the more frequently the rings meet on the same level.

We actually observe this from start to finish with RNA viruses, which sometimes evolve extreme virulence and exterminate broad swathes of their host species. Moreover, they are so simple, reproduce in such vast numbers, and mutate so rapidly that the evolution of virulence is consistent with microevolution* alone. Yet despite RNA viruses repeatedly taking a shotgun to the host species' fitness landscape, the host survives and indeed thrives because it has not converged to a single "perfect" fitness peak.

*Logic and strong evidence have forced many anti-evolutionists to accept microevolution, the idea that individual single-nucleotide mutations affect fitness, and will cause some sort of genetic drift even if intelligent intervention is needed for major biological innovation.

If we posit gigantic Calvinist selection pressure—selection Heaven for beneficial mutations, selection Hell for deleterious mutations—the landscape would be perfectly smooth, with the aggregate Terran genome slowly oozing along a gentle slope in whatever direction up currently happens to be. And that is a far more interesting subject than macroevolution, from a theological point of view. Does the global landscape have local maxima at which Earth-descended life can become trapped? Should Man accept those lesser peaks as a natural limit? Should he strike out across the valleys for an unknowable Genetic Promised Land? It's a pity that certain theologians have become stuck at their own local maximum of interesting things to talk about.

I wonder, were there any medieval scholars who argued vehemently about how many angels could dance on the head of a pin without understanding it was an allegory?

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