> How would such a mutation help her lineage? But that same question, more broadly, how do mutations that benefit people past their child bearing age factor int

> How would such a mutation help her lineage? But that same question, more broadly, how do mutations that benefit people past their child bearing age factor into human evolution? To oversimplify a bit, you can think of most mutations as neutral, in terms of reproductive fitness. People (and populations) accumulate them all the time, just by chance. Occasionally, one that was previous neutral becomes beneficial when the environment changes - say, when it confers immunity to a virus, or helps with synthesizing an amino acid that's in short supply. This is why having a big population with lots of variation is beneficial and why bottlenecks hurt the viability of a species.