>>16703014
One of the problems may be that we are actively designed to age and die by our biology. If human beings didn't and were biologically immortal then you'd have a population dominated by postmenopausal women and men who had already reproduced who knows how many times (therefore limiting the gene pool) and who now have declining sperm quality. You may also have biological features that kill us early but give us an advantage in our reproductive years so they're still spread.
Imagine, say, a trait that increases your chances of getting lung cancer and makes it more aggressive once you hit your 60s and beyond, but in exchange it means you can absorb more oxygen and use it more efficiently. This means making you slightly smarter and stronger, improving your general health, making you hold your breath longer, etc. Even though this kills you quicker it would still be an advantageous trait and get passed down because it would still be beneficial throughout a woman's reproductive years and through a male's primary reproductive years. It's not impossible that human biology has countless little traits like that
