From an evolutionary perspective , human menopause does n’t make a mountain of common sense . Searching for an explantion for this somewhat unambiguously human process , a mathematical group of Canadian investigator used computer models to show that menopause is an unintended outcome of innate pick — and men ’s sexual preferences might be to blame .
No doubt , change of life , or generative ageing , is a strange biologic phenomenon . Virtually every female creature on Earth stay on reproductive until the day she dies . Among mammals , hulk have been follow to give birth into their 80s , and elephant into their 60s . Other than humans , the only animals to experience menopause appear to besomewhalesandcaptive chimpanzees . The question that scientists have been asking , therefore , is why humans have such a pronounced postmenopausal survival stage .
Biologists have come up with a bunch of theory to excuse menopause , admit the gran theory — the approximation that women evolved eld - induced infertility to help them assist with the breeding of their grandchild . At a certain storey this makes sense ; it ’s a summons that ameliorate the opportunity of their kin surviving . Interestingly , the grandmother hypothesis may also be responsible for human longevity .
https://gizmodo.com/computer-simulation-confirms-it-was-grandma-who-gave-us-5954427
There are at least nine other theory that seek to excuse human menopause , including the lifespan - artefact hypothesis ( it ’s a consequence of human length of service ) and the paterfamilias hypothesis ( the origin of change of life allowed men to mate with younger women , resulting in increase longevity ( for both gentleman’s gentleman and womanhood ) and increased status in lodge ) .
But this last guess fails to excuse why climacteric evolved in the first position — and this is where thenew study , which was published today in PLOS Computational Biology , comes in .
harmonize to computing machine modeling set up up by Rama Singh , Richard Morton , and Jonathan Stone of McMaster University in Hamilton , Ontario , contest among human being of all eld for younger women left older females with a atrophied opportunity of reproducing . Over time , innate survival protects natality in adult female — but only when they are most likely to reproduce . The researchers ’ simulations showed that male mating predilection for younger females resulted in the accruement of injurious mutations that negatively bear on fertility among older female . The final result : the advent of menopause in the human mintage .
To fly the coop the simulation , the researchers trust on two primary assumption . First , that there was a shift of virile preference toward younger female . And second , that there are female - specific chromosomal mutation with detrimental effects on richness in older women ( e.g. hormonal changes , oocyte depletion and ultimate red ink , ovulation cessation , menstruation endpoint , and so on ) .
After running the simulation over a hundred time , the researchers systematically go through that the older distaff simulants finally acquired enough mutations to result in the evolutionarily acquire condition of menopause .
Interestingly , according to this theory , if men did n’t prefer younger female person , adult female of all ages would still be able to procreate . Also , if the tendency were reversed , and it was women who preferred younger Male , then fertility among aged males , instead , would have been compromised .
Needless to say , the consumption of computers to sympathize evolution , while interesting , is a wholly unequal approach . Yes , the conditions ready up in the simulation result in the menopause effect , but that does n’t necessarily mean that existent life organic evolution occurred in the accurate same style .
At the same time , given tough competition among males for females , it ’s not unreasonable to indicate that many males would still look for old females ( including , and peculiarly , older male person ) . Why older females should have been simply been left out does n’t make a whole plenty of gumption . The only thing I can intend of is that females might have been the ones to opt older males ( i.e. female driven intimate selection ) , or that the older males held back the young males from pair .
Moreover , the researchers have not satisfactorily dismiss the other predominate theories , including the lifespan - artefact hypothesis and the ageing hypothesis . Humans do in fact populate extraordinarily long lives , and it ’s quite possible that fertility is but one of the first things to go ; life goes on , but fecundity does not . At least in Homo sapiens . It is , after all , a rather complex biologic appendage . More study needs to be done in this area .
Lastly , given that menopause has been documented in whale and chimps , it would be worth doing a work on those animals to see if the males of those species also prefer young females .
record the full subject area at PLOS : “ Mate Choice and the Origin of Menopause . ”
Top figure of speech : It ’s Rude to Stare .
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