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Promiscuous females stall male extinction, according to a new study on fruit flies.

Scientists at the University of Liverpool discovered flies in the northern parts of the United States are more promiscuous. Mating with several partners helps reduce the occurrence of an X chromosome that leads to the production of only female offspring, according to researchers.

Researchers said that this selfish genetic element (SGE) tries to replicate itself by killing sperm that carry the Y chromosome. One detrimental side effect of this selfish genetic element is that males with the gene tend to produce fewer sperm. Researchers believe that female fruit flies take advantage of this weakness by mating with several partners to increase the probability of reproducing with SGE-free males with higher sperm count.

The latest study showed a strong correlation between the number of mates and the prevalence of the gene by gathering samples of fruit flies from seven sites in the United States.

Previous studies have already revealed that southern population of the fly had a higher prevalence of the gene compared to their northern counterparts. Therefore, researchers hypothesized that this was because northern flies are more promiscuous.

The current study revealed that when females were only allowed to mate once, the SGE gene spread rapidly enough through populations to drive them extinct in only nine generations.

"If this particular SGE was to spread to every male in a population, then no more males would be born, and the population, or even the whole species, would become extinct," Evolutionary biologist Dr. Tom Price from the University of Liverpool's Institute of Integrative Biology, said in a university release.

The study also revealed that northern flies were more likely than southern flies to mate more often. Northern flies were also prepared to mate against significantly more quickly than southern flies. Researchers explain that a combination of this type of behavior is more effective at limiting the spread of SGE.

"There are a large number of these SGE genes in many organisms, which selfishly increase their own success while damaging the health of individuals and the species as a whole, but in this case the flies have developed mechanisms to limit their impact," Price explained. "Females with a high sex drive and males with a high sperm count are keeping this species going."

The findings are published in the Proceedings of the Royal Society.