You're only 1/4 related to grand children. A strategy of living a long life to help raise a grandchild means that 3/4 of your effort is promoting someone else's genes. Now what if the strategy of those other people is to have many more children, possibly with many different partners, with a relatively diminished per-child investment, reliant on someone like you to help raise those children. Who's going to out-compete whom?
I'm not saying the second strategy is better, just pointing out that the first strategy is self-limiting. Which means we can't even begin to understand the benefits and viability without answering more complex questions; questions we don't yet have answers to.
Also, humans are the only known species, extant or extinct, which exhibits significant non-kin altruism.[1] There's no strong theory for how this emerged. Which means there are some very important dynamics to human evolution (and evolution in general) that we're completely ignorant to--we don't even know what the questions are, let alone the answers.
[1] The most popular mammals used for comparison to humans, bonobos and naked mole rates, are organized as matriarchies--the females are sisters, somewhat like ants and bees. The above-average altruism they exhibit is easily explained by basic Darwinian genetic evolutionary theory.
> You're only 1/4 related to grand children. A strategy of living a long life to help raise a grandchild means that 3/4 of your effort is promoting someone else's genes.
But you are helping to raise 100% of your descendants. I'm not sure it is relevant that your descendants have less genetic material in common with you as you move down the tree.
> Now what if the strategy of those other people is to have many more children, possibly with many different partners, with a relatively diminished per-child investment, reliant on someone like you to help raise those children. Who's going to out-compete whom?
The premise of Idiocracy! In this scenario, though, there could still be benefits of some per-descendant investment. I'm not sure "high investment in few offspring vs. low investment in many offspring" debate really matters to the question of "why stay alive longer than (age of infertility)+(maturation time of offspring)".
I think the answers lie in 'group selection'. Not sure how accepted a theory that is though. An example I've heard (but can't find reference to now) is that the tonsils may serve to kill off sick individuals before they can infect others.
I'm not saying the second strategy is better, just pointing out that the first strategy is self-limiting. Which means we can't even begin to understand the benefits and viability without answering more complex questions; questions we don't yet have answers to.
Also, humans are the only known species, extant or extinct, which exhibits significant non-kin altruism.[1] There's no strong theory for how this emerged. Which means there are some very important dynamics to human evolution (and evolution in general) that we're completely ignorant to--we don't even know what the questions are, let alone the answers.
[1] The most popular mammals used for comparison to humans, bonobos and naked mole rates, are organized as matriarchies--the females are sisters, somewhat like ants and bees. The above-average altruism they exhibit is easily explained by basic Darwinian genetic evolutionary theory.