Title Author Date

Meyer's Helpless Monster Elsberry, Wesley R. Apr 11, 2005

Math is a wonderful tool, but when one insists that reality must be a certain way because of the math, it doesn't help one's position if reality refuses to play along. It is reality that sets the score and math that has to sing to it or be considered off-key.

Nobody is "hiding" segregational load. The genetics text used in my college course a couple of decades back (Strickberger's "Genetics") has a quite forthright discussion of the problems of asserting selective maintenance of large numbers of polymorphisms via heterozygote advantage. It is, in fact, one of the issues that led to the development of the "neutral theory" by Kimura and Crow. Under the neutral theory, the rate of allelic substitution in a population is linked to the mutation rate. Because selection is not operating, neutral evolution proceeds at rates that, in summation, exceed what is possible via selection at many loci. And there is plenty of math to go with the neutral theory and its more recent derivative, the "nearly neutral" theory.

That said, when one looks at real world populations, one commonly finds that alleles are in linkage disequilibrium, which is indicative of the action of natural selection. No matter how much math is deployed, the facts on the ground indicate that natural selection does actually happen in biological populations.

What we are left with are two rock-bottom empirical phenomena that any mathematical model must account for: 1) Biological organisms typically have a lot of genetic variation, one measure of which is the level of protein polymorphism in a population, usually not less than 20 to 30 percent of proteins showing polymorphisms and 2) many populations show the presence of linkage disequilibrium indicating active selection for some trait or set of traits. We can be sure that math that tells us that this situation cannot exist has a flaw in the premises somewhere.

Together, these facts argue strongly that both neutral evolution and natural selection are operative in extant populations. The question is how much of evolutionary change does each account for.

A nice page answering antievolution arguments on "Haldane's dilemma" is at this page.

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