Published online by Cambridge University Press: 15 June 2005
If alleles that predispose to schizophrenia have reduced Darwinian fitness, their persistence in modern times is puzzling. Burns identifies the evolutionary genetics of schizophrenia as a central issue, but his treatment of it is not clear. Recent advances in evolutionary genetics can help explain the persistence of alleles that predispose to debilitating disorders such as schizophrenia, and can buttress Burns' core argument.
1. “Allele” is used broadly here to include not only genetic variants in the protein-coding regions within loci, but also genetic variants in the regulatory regions that surround loci.
2. In a large, randomly breeding population, the expected frequency (q') for the susceptibility allele after one generation of selection is given by the recursive equation
where q is the frequency of the susceptibility allele before selection, p is the frequency of all other alleles at that locus before selection, and w1 and w2 are the fitnesses of those carrying one or two susceptibility alleles, respectively, relative to those carrying no susceptibility alleles. (MATLAB script iterating this equation available from the author on request.)