Promiscuous birds produce genetically stronger offspring, study shows
New research shows that when female birds mate with multiple partners, they produce genetically stronger offspring.
Published Sep. 3 in the journal Proceedings of the Royal Society B, the study looked into the mating practices of red junglefowl, the wild ancestor of the domestic chicken. The University of East Anglia researchers found that promiscuity maximized the female junglefowls' chances of having offspring that are resistant to diseases.
The reason promiscuity matters here is that the sperm of various mates can remain viable inside the female. An internal mechanism called "cryptic female choice" then allows the reproductive tract to favor the sperm from males that are most genetically different from the female, according to a press release.
"Our research has shown that the females don't need to choose between males to produce the most healthy offspring," said Professor David S. Richardson of UEA's school of Biological Sciences. "Rather by mating with multiple males, they allow their internal choice mechanism to favour the most genetically different sperm."
The genes that they stand to gain are part of the major histocompatability complex, which plays a key role in detecting and fighting infection. When the female reproductive tract selects for sperm that carry different genes, the resulting offspring are that much more capable of fighting off disease.
The researchers expect to find similar gene selection at play in other species and animals, possibly even humans. But promiscuous ladies and gents, don't get too excited: they won't be proving the benefits in humans anytime soon.
"This could be the case in other animals -- including humans, however the practicality of testing this in mammals would be very difficult, and obviously impossible in humans for ethical reasons," Richardson said.
In the study, the researchers tested controlled natural matings as well as artificial insemination. The stronger gene effect was lost during artificial insemination, which could mean that breeding disease-resistant animals will not be as easy as they initially hoped.
"Many breeding programmes for livestock and conservation use artificial insemination. But our research suggests that this may not produce the best quality offspring," the author said. "This is because the effect appears to require the subconscious female assessment of the male by some cue during actual mating."
In other words, when it comes to breeding, Mother Nature still knows more than Sister Science.
