With your coffee … With human evolution studies, we sometimes get valuable, though elusive clues (the role of Neanderthals in the human heritage), and then other times we get “‘Stay-at-home’ males fueled menopause evolution“:
One of the most popular explanations put forward for the menopause is the ‘grandmother hypothesis’, which suggests that women live long past reproductive age in order to help successfully raise their grandchildren, thereby strengthening the likelihood that their own genes are passed on. Others argue that the menopause offers no selective advantage and is an evolutionary fluke or ‘mismatch’ which arose because humans were designed for shorter lifespans but now live much longer.
“Designed” for shorter lifespans? Yes, that is what it says. Someone, call Darwin 9-11.
Evolutionary biologist, Dr Kevin Arbuckle, from the University of Liverpool, said: “Our results suggest that the menopause arose through a non-adaptive ‘mismatch’ between lifespan and reproductive span. Subsequently we think that in populations where males remained at home and females dispersed to reproduce, an adaptive benefit drove the extension of this post-reproductive period.
“This adaptive benefit could have come from grandmothers looking after their sons and grandsons at home. As females tend to reproduce more reliably than males, this additional family support could have made it more likely that their grandsons successfully reproduced. “More.
Could have is not science. The space aliens could have landed and left no trace.
One sometimes wonders whether “menopause” means anything more than that a female of any species outlives her reproductive potential. That probably doesn’t happen most of the time, which makes serious study difficult. But as the perennial institution of the hen party will attest, the subject continues to interest many.
Unfortunately, some of them are Darwinian evolutionary biologists:
In reality, patterns in life forms are often wrongly interpreted when Darwinism is used as a frame. For example, current evolutionary theory provides no clear basis for interpreting a relationship between longevity and fertility. Thus, some researchers claimed that women undergo menopause but chimpanzees do not, that “menopause is not a part of the life cycle of living apes but has been uniquely derived in the human lineage.”
Darwinian explanations for that are, of course, on offer. For example, men triggered menopause (by preferring younger women). Or women’s selfish genes cause them to forego future breeding in order to invest in the survival of their existing selfish genes (children), sometimes called the grandmother hypothesis. That thesis assumes, of course, that older women are an asset to a group. Sometimes they are, sometimes not.
Despite all such claims, chimpanzees do undergo menopause, as a carefully researched 2012 paper on captive chimpanzees notes. But she-chimps do not typically live long after menopause. A recent article in Nature summarizes the fact that current evolution theory provides no basis for interpretation of the relationship between longevity and fertility in life forms.
See also: “I married a Neanderthal!” It doesn’t sound like we know much about these early unions, and there will doubtless be surprises to come.
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