Point #4: Your genes only care about your survival insofar as it helps you to reproduce. Point #5: Old age is a side benefit of reaching childrearing age, but none of that matters unless fertilized eggs are perfectly fresh every single generation.
Have you heard of the grandmother hypothesis?
I don’t think humans are bunnies where we accidentally live far past reproductive age and e.g. have menopause
The reason I didn’t include material on the grandmother hypothesis is not covered in this 8-page chapter. It’s not a key feature of most of the research on decreasing selection pressure with age, which assumes the overwhelmingly most important contribution to the germ line is via reproduction rather than nurture.
The grandmother hypothesis is mainly attempting to explain menopause, which is indeed an evolutionary mystery.
The ability of parents to provide nurture, and the difficulty of producing survivable large offspring, drives some organisms, like humans, away from a K-selection strategy (lots of offspring, small short-lived organisms, aiming for a few survivors) toward an R-selection strategy (a few offspring, large long-lived organisms, aiming for high likelihood of survival and reproduction in all offspring). But raising reproductive age, which enforces pressure for long life and thus the tendency for R-selected organisms to reach an older age, is an evolutionary cost. If evolution could engineer humans to become reproductively fertile at age 3 without any other costs, it would do so.
In R-selection, evolution is sacrificing opportunities to produce more young at a younger age in exchange for greater survivability and the ability to exploit new sources of energy. That can push reproductive age up, as we see in humans, and the effort to build us robustly enough to ensure we reach that later reproductive age both raises the likelihood we live much longer and allows surviving grandparents to confer benefits on the young, the latter of which is a straightforward adaptive “win” from a gene’s perspective.
But my take is that whatever nurture grandparents can provide is a side benefit that doesn’t change the overwhelming evolutionary pressure to make ~all tradeoffs favor the young, meaning that the arguments from antagonistic pleiotropy and limited/loss of selection pressure in old age still apply with full force. That is an encouraging take, because it means that there’s plenty of scope for modern medicine to improve healthspan and lifespan—not to mention that there are plenty of things we can do using technology that are just not evolutionarily accessible. For example, we can build mechanical replacements for our organs, design and manufacture molecules arbitrarily with a much greater level of purity and under more controlled conditions, and of course we can eliminate threats and artificially extend the age of first reproduction in ways that tend to drive evolution toward longer life and healthspans.
Have you heard of the grandmother hypothesis?
I don’t think humans are bunnies where we accidentally live far past reproductive age and e.g. have menopause
The reason I didn’t include material on the grandmother hypothesis is not covered in this 8-page chapter. It’s not a key feature of most of the research on decreasing selection pressure with age, which assumes the overwhelmingly most important contribution to the germ line is via reproduction rather than nurture.
The grandmother hypothesis is mainly attempting to explain menopause, which is indeed an evolutionary mystery.
The ability of parents to provide nurture, and the difficulty of producing survivable large offspring, drives some organisms, like humans, away from a K-selection strategy (lots of offspring, small short-lived organisms, aiming for a few survivors) toward an R-selection strategy (a few offspring, large long-lived organisms, aiming for high likelihood of survival and reproduction in all offspring). But raising reproductive age, which enforces pressure for long life and thus the tendency for R-selected organisms to reach an older age, is an evolutionary cost. If evolution could engineer humans to become reproductively fertile at age 3 without any other costs, it would do so.
In R-selection, evolution is sacrificing opportunities to produce more young at a younger age in exchange for greater survivability and the ability to exploit new sources of energy. That can push reproductive age up, as we see in humans, and the effort to build us robustly enough to ensure we reach that later reproductive age both raises the likelihood we live much longer and allows surviving grandparents to confer benefits on the young, the latter of which is a straightforward adaptive “win” from a gene’s perspective.
But my take is that whatever nurture grandparents can provide is a side benefit that doesn’t change the overwhelming evolutionary pressure to make ~all tradeoffs favor the young, meaning that the arguments from antagonistic pleiotropy and limited/loss of selection pressure in old age still apply with full force. That is an encouraging take, because it means that there’s plenty of scope for modern medicine to improve healthspan and lifespan—not to mention that there are plenty of things we can do using technology that are just not evolutionarily accessible. For example, we can build mechanical replacements for our organs, design and manufacture molecules arbitrarily with a much greater level of purity and under more controlled conditions, and of course we can eliminate threats and artificially extend the age of first reproduction in ways that tend to drive evolution toward longer life and healthspans.