Comment by rlpb
> ...a really hard problem that evolution has spent billions of generations on...
I think it's worth noting that this isn't evolution's "goal". We just need to produce offspring and give them a good start in life such that they are competitively successful. Beyond that, evolution doesn't care.
Even for that, there's a budget. If it's not economical over letting us die and not taking valuable resources from our offspring, then evolution also doesn't care.
That could suggest why longevity in humans (or primates ) was under active selection, as they put a lot of effort into raising the children so you'd expect that cancer in younger people would result in the death of their children, so evolution selects for robust anti-cancer systems (like the human immune system, which is relatively good at detecting and eliminating cancer cells as well as pathogenic bacteria, etc.).
These explanations are however always a bit hand-wavy, eg why do galapagos tortoises live to 150 when they don't seem to do much parental investment?