DNA shows evidence of sexual selection

ESTIMATING THE STRENGTH OF SEXUAL SELECTION FROM Y-CHROMOSOME AND MITOCHONDRIAL DNA DIVERSITY

We show that a sex difference in the opportunity for selection results in sex differences in the strength of random genetic drift and thus creates different patterns of genetic diversity for maternally and paternally inherited haploid genes. We derive the effective population size Ne for a male-limited or female-limited haploid gene in terms of I, the “opportunity for selection’ or the variance in relative fitness. Because the variance in relative fitness of males can be an order of magnitude larger than that of females, the Ne is much smaller for males than it is for females. We derive both nonequilibrium and equilibrium expressions for FST in terms of I and show how the portion of I owing to sexual selection, Imates, that is, the variation among males in mate numbers, is a simple function of the F’s for cytoplasmic (female inherited) and Y-linked (male inherited) genes. Because multiple, transgenerational data are lacking to apply the nonequilibrium expression, we apply only the equilibrium model to published data on Y chromosome and mitochondrial sequence divergence in Homo sapiens to quantify the opportunity for sexual selection. The estimate suggests that sexual selection in humans represents a minimum of 54.8% of total selection, supporting Darwin’s proposal that sexual selection has played a significant role in human evolution and the recent proposal regarding a shift from polygamy to monogamy in humans.

I’m going to point out that selection works much harder on males than females, as historically more women than men have had children (successful men have more children, losers have less).

A factor of many mixed ancestry populations is that you’ll see the  Y chromsomes of the dominant group over represented compared to the mtDNA. This is typical of a population where a one population has  subjugated another, essentially replacing the ‘defeated’ males with varying levels of success. Whether this counts as sexual selection according to the authors of this, I don’t know.

You see this pattern in South America, where there there are a rather larger percentage of mtDNA haplotypes (is indigenes a word?) than Y chromosomes from the aboriginal population.

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