Promiscuous Moms Have Sexy Sons -- in Mice, At Least

Who knew?  But moms who have a lot of sex partners have sexier male children.  We're talking mice, of course.

At least that's what a new study has found, according to "University of Utah biologists found that when mother mice compete socially for mates in a promiscuous environment, their sons play hard (read: make lots of babies) and die young," according to the Web site.

The male mice attract more females by making more urinary pheromones, but smelling sexier shortens their lives. (Not sure this would work for humans.)

“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,” quotes biology professor Wayne Potts, senior author of the new study.

Yet there's no faking that male mice who create more baby mice run out of life more quickly.  In the study, only 48 percent of these hard-working mice lived to the end of the experiment, compared with 80 percent of the male mice whose parents lived monogamously in cages, probably because, notes, it takes so much energy to produce the sex attractants, which are secreted in urine and from certain glands.

Hey, it may be fun but it can really wear you out.

Not sure if it holds true for humans (at least it hasn't been studied yet), but male mice with promiscuous parents actually produce about one-third more progeny than sons of monogamous parents, previous studies have shown. Female mice prefer scent marks saturated with pheromones produced in mouse urine and other glands, and they mate more often with males who produce such marks.

“Pheromones are the language of mice,” says the study’s first author, former University of Utah doctoral student Adam C. Nelson at “When females mate in a socially competitive environment, they program their sons to have a head start by producing more pheromones.”

But here's the killer. Dads make sons less sexy.  Why?

Mice in the lab, unlike in the wild, are typically caged with just one mate, so they breed monogamously. But for the study, mice were placed in mice barns, which allowed them to roam and find mates, as many as they wanted.  Regardless of the dad’s original environment (promiscuous or monogamous), sons of moms from a promiscuous, social environment produced more pheromones than sons of monogamous, domesticated moms, highlighting the mom's interest in passing her genes to the next generation.

But dads from the promiscuous, socially competitive environment had a surprising negative influence on their sons’ sexual attractiveness. Those sons produced 5 percent fewer pheromones than sons of monogamous fathers, explains.

“Fathers are competing with their sons and usually drive them out of the territory quickly, while they let daughters stay,” says biology professor Wayne Potts, senior author of the new study. “If you're worried about your sons impinging on your own reproductive success, then why make them sexy?” 

Kind of like dads who go after girls their own sons' age.  They just want to get there first.


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