Antagonistic pleiotropy may help make babies

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In direct contrast to the previous post, which preaches caution when attributing antagonistic pleiotropy to cases where palpably deleterious genes or gene variants persist despite their obvious dysgenic effects, this paper, in Proceedings Of The Royal Society B, by Grazyna Jasienska et al, uncovers a very plausible solution to why the deleterious APOE epsilon 4 gene variant persists at high frequency in modern populations despite the fact that it is linked to a 40% increased risk of cardiovascular disease and is THE major risk gene for Alzheimer’s disease, increasing the chances of carriers contracting Alzheimer’s by some fifteen times. The authors make the case that the compensating value of APOE E4 lies in increased production of the female sex hormones estrogen and progesterone which links to higher fertility. They conclude: “We show that women with the ApoE4 allele have higher levels of progesterone during the menstrual cycle, and this finding suggests, albeit indirectly, an evolutionary reason for maintaining the ancestral ApoE4 allele in the human populations, because ApoE is a major supplier of cholesterol precursor for the production of steroid hormones.”