Beth asks:
"Ah! Reproduction. But how about in later years?"

From a biological standpoint we are expendable as soon as you no longer can reproduce. And if one looks at the vast majority of human history, with life expectancies in the 30s - 40s, that is precisely what happened.

Were it not for modern medicine in the last couple of hundred years ... that would still be the case for the vast majority of those born.

DA Morgan