Having more sex produces a longer manhood–at least in beetles, according to a provocative new study.
It took about 10 generations for male burying beetles to sprout longer penis-like structures, and females experienced changes too — larger “claws” on their corresponding parts, scientists at the University of Exeter found.
“It takes two to tango, so when changes in shape in one sex leads to corresponding changes in the other sex this is known as co-evolution,” according to Megan Head, one of the study’s authors.
Frequent fornication benefits males more because it increases the number of offspring he is likely to produce. But females– from bears, to bison to beetles– only need to do the deed a few times to fertilize all her eggs, according to the authors.
Too much sex also can be costly for females because it reduces their ability to provide parental care.
To test whether this so-called “sexual” conflict does in fact lead to co-evolutionary changes in the shape of genitalia, the researchers artificially selected pairs of beetles for either high mating rates, or low rates for 10 generations, according to the study, published in journal Evolution.
The researchers found the greatest shape changes occurred in beetles selected for high mating rates, where sexual conflict was greatest — but they couldn’t yet explain why.
“Although we don’t know the ins and outs of how these genital structures relate to the reproductive success of each sex, our results show that sexual conflict over mating can lead to co-evolutionary changes in the shape of the genitals of burying beetles,” the university’s Paul Hopwood said.