Comment by derbOac

I've read it's not so much that a particular aging trajectory is selected for, it's that mechanisms that shorten lifespan aren't selected against depending on ecology, social structure, and so forth. I imagine that's not entirely accurate, though, as there are some species that have definite senescence patterns that are closely tied to important developmental events (e.g., octopuses and egg laying).

It's difficult for me to imagine something that selects for individual death per se, but I can imagine certain cellular repair mechanisms and so forth, with death at a certain age being a secondary consequence, being selected for depending on a host of factors. Evolution tends to be somewhat chaotic in that what's adaptive depends on prior evolutionary history to some extent.