It is an event that affects all members of the fairer sex when they reach a certain age, but now women going through the menopause may have someone to blame for their life change - men.
Scientists claim that the menopause, which is thought to be unique to humans,
may have evolved due to a preference among men to breed with younger women.
A study using computer modelling to assess how such a preference would have
driven evolution has now given some weight to the theory.
Professor Rama Singh, from Canada’s McMaster University, said that competition
between men for younger mates had left older females with less chance of
reproducing.
He said: “Menopause is believed to be unique to humans, but no one has yet
been able to offer a satisfactory explanation for why it occurs.
“How do you evolve infertility? It is contrary to the whole notion of natural
selection. Natural selection selects for fertility, for reproduction.”
Scientists have proposed a number of hypotheses for why women may go through
the menopause, where they under go hormonal changes and their ovaries stop
producing eggs.
Among the ideas put forward is the so called “grandmother theory”, where women have evolved as part of social groups where older women cooperate to help rear their grandchildren.
However, the work by Professor Singh, which is published in the journal PLOS Computational Biology, suggests that it was the preference of men for younger mates that drove the process.
This would have meant that provided women were fertile at younger ages, it did not matter that they then later became infertile and so mutations that brought on the menopause would have persisted and become more prevalent over time.
This, however, not only brought the loss of fertility for women, but also an increased risk of disease and death in later life.
Prof Singh added, however, that if menopause developed over time in this way, it could also be reversed.
Dr Maxwell Burton-Chellew, evolutionary biologist at the University of Oxford, said the study did not explain why the menopause is so rare in the animal kingdom.
He said: “The authors argue that the menopause exists in humans because males have a strong preference for younger females.
“However, this is probably the wrong way round - the human male preference for younger females is likely to be because older females are less fertile.
“Even if this study is correct, it fails to explain why the menopause is so rare in the animal kingdom.
“The menopause is unlikely to just be a by-product of evolutionary forces, but rather it is probably best understood as an adaptation that was advantageous to women.”
Among the ideas put forward is the so called “grandmother theory”, where women have evolved as part of social groups where older women cooperate to help rear their grandchildren.
However, the work by Professor Singh, which is published in the journal PLOS Computational Biology, suggests that it was the preference of men for younger mates that drove the process.
This would have meant that provided women were fertile at younger ages, it did not matter that they then later became infertile and so mutations that brought on the menopause would have persisted and become more prevalent over time.
This, however, not only brought the loss of fertility for women, but also an increased risk of disease and death in later life.
Prof Singh added, however, that if menopause developed over time in this way, it could also be reversed.
Dr Maxwell Burton-Chellew, evolutionary biologist at the University of Oxford, said the study did not explain why the menopause is so rare in the animal kingdom.
He said: “The authors argue that the menopause exists in humans because males have a strong preference for younger females.
“However, this is probably the wrong way round - the human male preference for younger females is likely to be because older females are less fertile.
“Even if this study is correct, it fails to explain why the menopause is so rare in the animal kingdom.
“The menopause is unlikely to just be a by-product of evolutionary forces, but rather it is probably best understood as an adaptation that was advantageous to women.”
0 comments:
Post a Comment