Promiscuous mouse moms have sexy sons
Female mice with multiple sexual partners have sexy sons, according to a new study from the University of Utah published in the Proceedings of the National Academy of Sciences on Wednesday. The male offspring of promiscuous females gave off stronger sex pheromones than the descendents of mice with only one partner.
“If your sons are particularly sexy, and mate more than they would otherwise, it’s helping get your genes more efficiently into the next generation,” said Wayne Potts, biology professor at the University of Utah and senior author of the study. “Only recently have we started to understand that environmental conditions experienced by parents can influence the characteristics of their offspring. This study is one of the first to show this kind of ‘epigenetic’ process working in a way that increases the mating success of sons.”
The researchers at the University of Utah raised ten generations of mice in groups of monogamous mice – 23 male-female pairs – and promiscuous mice – 20 males and 40 female, which competed for partners and territory. Then mice bred in four combinations: mother and father from promiscuous environment; both from monogamous environment; mother from promiscuous environment and father from monogamous environment; and vice versa.
The sons of promiscuous females produced 31 percent more urinary pheromones than the offspring of the domesticated pairs. But the male lotharios had the opposite effect on their sons. Potts and his team found that sons from polyamorous fathers inherited 5 percent fewer pheromones than the offspring of monogamous dads.
“Fathers are competing with their sons and usually drive them out of the territory quickly, while they let daughters stay,” says Potts. “If you’re worried about your sons impinging on your own reproductive success, then why make them sexy?”
Male mice with stronger pheromones attracted more female mates, and sired a third more babies. But a sexier smell meant the mice play hard and die young, Potts said. Only 48 percent of those mice lived to the end of the experiment, compared to 80 percent of the sons of monogamous pairings.
Understanding how a parent’s social environment shapes genetics could make a difference in reintroducing captive species to the wild. Often captive-bred animals fail to compete with their wild counterparts for mates as well as territory, and knowing how something like pheromone production changes with environment may improve their success rates.
“It’s amazing how often reintroduction of captive-breed endangered species fails – it’s estimated to be as high as 89 percent,” says Potts. “Domestication stimulates epigenetic mechanisms that make animals less fit for nature.”