just-shower-thoughts:
Cave woman would have not known about the menopause until the life expectancy increased. Maybe there is another human hormonal change that we are not aware of as we have not reached the particular age it happens.
Totally incorrect! Actually, the fact that human females live past their reproductive life span is responsible for a great deal of human evolution, especially the ways in which we differ from our close ape relatives. This is called the Grandmother hypothesis.
Let me explain.
So the idea that human life expectancy has increased due to modern advancements is a myth. The average life span has certainly increased, however this is not because humans live longer (we have always lived to around 70-90yrs), but because infant mortality has decreased. In other words, modern medicine and abundant access to resources have decreased how how many children die, therefore increasing the average years humans live past birth.
So, Humans have known about menopause since the beginning, and it’s actually a huge part of our evolutionary history. Other apes do not live past their reproductive life span, as their bodies degrade shortly after ceasing to be fertile- evolution is all about how many offspring can be produce after all. Its generally a waste of resources to continue feeding adults who cannot reproduce when fertile adults and children are competing for those same resources.
So the fact that human females live for upwards of 30yrs past fertility was considered an evolutionary paradox. The key is that humans are really smart (sort of). We require a very long time to develop our brains, and so our infants are completely useless- unable to evan walk for a year, much less feed or protect themselves until middle childhood. They require a lot of attention and caring for, constant vigilence, not to mention hours spent teaching them basic survival tasks.
As a result, humans developed cooperative childraising systems, in which members outside of the child’s immediate family are responsible for caring for the young. However, if all the adults are busy raising their own children, no one would ever care for anyone else’s, except the older, not-yet-fertile children (who do assume childrearing roles, but are still developing and therefore are not good at it.) As a result, the females who stayed alive past their reproductive life span, no longer responsible for their own children, were able to care for the children of their children, allowing for their genes to be passed down more successfully. This creates a positive feedback system in which females lifespan progressively increases, since the older the grandmother, the more children the mother is able to have, and the more successfully they will be raised to adulthood, passing on the genes for long life to their children in turn.
This effect however decreased with subsequent generations: it’s less economical to have a grandmother AND a great grandmother taking care of the young. The payoffs aren’t high enough to push our lifespans even higher.
Tldr; humans have always had unusually long lifespans BECAUSE menopause occurs, and this is an integral aspect of our evolution, causing us to be as intelligent and adaptive as we are.
Even better, one of the ways we know about the grandmother effect is because you also see it in orcas! They can live to 80, but generally stop breeding in their 30s. There are three known species that have this kind of menapause– us, orcas and the Short-Finned Pilot Whale (also another very social species).
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