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10/29/2007: "Promiscuity is de-evolutionary"
In a theoretical study published in the October 17, 2007 issue of Nature they demonstrate that sexual conflict can establish novel sex-determining genes and sex chromosomes. The proposed mechanism extends the established theory on the origin of sex chromosomes, and it explains how sex determination can move from an ancestral sex chromosome to an autosome, a non-sex-chromosome, that then invades to become a new sex chromosome.
The mechanism suggested by these authors begins with an autosome that carries two genes with particular features. One of these two genes is under sexually antagonistic selection. This means that some versions of the gene (alleles) are more beneficial in males than in females, while other alleles are more beneficial for females.
[ What made apes into humans? We were more sexually selective, which forced faster evolution. Promiscuity has the opposite effect and increases devolution.
http://www.sciencedaily.com/releases/2007/10/071019131411.htm