My cached mental explanation from undergrad when I was learning about the details of evolution and thinking about this was something along the lines of a heuristic like:
“Many plants and animals seem to have been selected for dying after a successful reproduction event. Part of this may be about giving maximal resources to that reproduction event (maybe your only one, or just your last one). But for animals that routinely survive their last reproductive event, and survive raising the children until the children become independent, then there’s probably some other explanation. I think about this with mice as my prototypical example a lot, since they seem to have this pattern. Commonly both male and female mice will survive reproduction, potentially even multiple cycles. However, mice do seem to be selected for relatively fast senescence. What might underlie this?
My guess is that senescence can cause you to get out of the way of your existing offspring. Avoiding being a drag on them. There are many compatible (potentially co-occurring) ways this could happen. Some that I can think of off the top of my head are:
Not being a vector for disease, while in a relatively weakened state of old age
Not feeding predators, which could then increase in population and put further stress on the population of your descendants / relatives.
Not consuming resources which might otherwise be more available to your descendants / relatives including:
Thanks for the cached explanation, this is similar to what I thought before a few days ago. But now I’m thinking that an older-but-still-youthful mouse would be better at avoiding predators and could be just as fertile, if mice were long lived. So the food & shelter might be “better spent” on them, in terms of total expected descendants. This would only leave the disease explanation, yes?
My cached mental explanation from undergrad when I was learning about the details of evolution and thinking about this was something along the lines of a heuristic like:
“Many plants and animals seem to have been selected for dying after a successful reproduction event. Part of this may be about giving maximal resources to that reproduction event (maybe your only one, or just your last one). But for animals that routinely survive their last reproductive event, and survive raising the children until the children become independent, then there’s probably some other explanation. I think about this with mice as my prototypical example a lot, since they seem to have this pattern. Commonly both male and female mice will survive reproduction, potentially even multiple cycles. However, mice do seem to be selected for relatively fast senescence. What might underlie this?
My guess is that senescence can cause you to get out of the way of your existing offspring. Avoiding being a drag on them. There are many compatible (potentially co-occurring) ways this could happen. Some that I can think of off the top of my head are:
Not being a vector for disease, while in a relatively weakened state of old age
Not feeding predators, which could then increase in population and put further stress on the population of your descendants / relatives.
Not consuming resources which might otherwise be more available to your descendants / relatives including:
food
good shelter locations
potential mating opportunities
etc
”
Thanks for the cached explanation, this is similar to what I thought before a few days ago. But now I’m thinking that an older-but-still-youthful mouse would be better at avoiding predators and could be just as fertile, if mice were long lived. So the food & shelter might be “better spent” on them, in terms of total expected descendants. This would only leave the disease explanation, yes?