A study has revealed that genes that act late in life could explain why women have poorer health than men in older age. Women are four times more likely to live to 100 years old than men, however, male who hits that milestone are healthier than female, according to a study.
The paper, published in the journal Nature Communications ‘Intralocus Sexual Conflict’ resolves a puzzle known as the “male-female health survival paradox.”
The answer, according to scientists from the University of Exeter in the UK, is “intralocus sexual conflict—genes that benefit one sex but harm the other.
“Shared genes tether the sexes together in an evolutionary tug of war,” said Professor David Hosken from the University of Exeter.
The researchers used mathematical models and experimental data on flies to show that such genes can easily spread if they take effect after female reproduction stops.
“Selection is trying to push females and males in different directions, but the shared genome means each sex stops the other from reaching its optima,” Hosken said.
“Basically, certain genes will make a good male but a bad female, and vice versa.
The researchers also explained as to why the centenarian men are healthier than women. Men who hit the milestone are considered the fittest because a greater proportion of men are diagnosed with chronic illness and die before hitting 100.
“However, after females reach menopause, they no longer reproduce to pass on their genes which means selection (which is a reproduction) on females is greatly weakened,” he said.
“So after that point, any genes that improve late-life male fitness will accumulate, even if they harm female fitness,” said Hosken.
He said it was important to note that survival and health are not the same thing—and that the accumulation of late-life male benefit genes hinged upon males’ ability to continue reproducing after the age of female menopause.
The experimental data on flies (Drosophila) supported the findings of the mathematical models on humans, as genes that were better at late-life male reproduction tended to be worse for females.
(With PTI inputs)