Mice with many sexual partners produce more fertile sons than do monogamous mice, providing a biological benefit of promiscuity, according to research published online today (January 20) in BMC Evolutionary Biology.
Image: Wikimedia commons
When a female mates with multiple partners -- a scenario called polyandry, which is common in mice -- sperm from rivals must face off to fertilize her eggs. This so-called "sperm competition" has been linked to the evolution of testes size, as well as sperm form and function, and promiscuity is believed to have evolved partly as a way for females to select genes for the highest quality sperm to pass onto her sons. But this is the first experimental evidence in mammals showing that promiscuity can affect the offspring's fertility. "I think [the new results are] an important confirmation of the evolutionary power of polyandry and the sperm competition selection that arises from polyandry,"...

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