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Menopause is evolution's way of solving the age-old tensions between wives and their mothers-in-law
Last updated at 06:52am on 03.04.08The menopause could be Nature's way of defusing tension between women and their mothers-in-law, scientists have said.
The hormonal change stops older women having children and competing for a larger share of an extended family's resources.
This leaves daughters-in-laws to concentrate on rearing any offspring instead.
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Hormonal: Scientists have found that the age-old tensions between wives and their mothers-in-law could be the reason for the menopuase
Michael Cant, a biologist at Exeter University, said: "When more than one female breeds, every mouth you feed is one less for your own.
"One of our characteristics is that we share food among family members, but having another female producing a baby means the offspring are competing for food and helpers for years.
"It it comes down to a choice between breeding and helping with other children, the younger women has nothing to gain, because she is not related to anyone in the group.
"But the older female can help to rear her grandchildren. It gives the younger female the advantage. She's going to breed no matter what."
Dr Cant's theory is published in the latest edition of the journal, Proceedings of the National Academy of Sciences.
He said that women experienced a rapid decline in fertility after the age of 40, culminating in the menopause around ten years later.
The study helps explain why rapid ageing of the reproductive system starts when it does, he added.
Earlier theories have held that the menopause evolved to ensure women care for their grandchildren.
Studies show that having a grandmother at hand greatly increases a baby's chance of survival.
The grandmother also benefits by safeguarding the survival of her genes.
