Why Do Humans Age? Hint: Evolution Doesn’t Care If We Live Past 40

InnovationScienceWhy Do Humans Age? Hint: Evolution Doesn’t Care If We Live Past 40ByScott Travers,Contributor.Forbes contributors publish independent expert analyses and insights. I write about biodiversity and the hidden quirks of the natural world.Follow AuthorApr 23, 2026, 08:30am EDT--:-- / --:--This voice experience is generated by AI. Learn more.This voice experience is generated by AI. Learn more.Human aging is not what natural selection failed to prevent. It is what happens when selection simply has nothing left to act on.gettyThere’s something unsettling about the fact that the human body starts deteriorating once you reach your late twenties — and doesn’t stop. Your muscle mass declines. Your DNA repair rate slows down. Cellular waste accumulates in places it wouldn’t previously. Most people treat aging as a fact of biological humanity, which you eventually have to learn to accept. But for an evolutionary biologist, aging is something stranger and more interesting than mere wear and tear. In many ways, it’s actually paradoxical.Natural selection, after all, is ruthlessly good at its job. Over millions of years, it has sculpted organisms of staggering complexity, such as the vertebrate eye, the immune system, even the migratory precision of the Arctic tern. So why, after all that fine-tuning, did it leave aging on the table? Why didn’t evolution simply fix, or at the very least, optimize aging?The short answer, as researchers Daniel Fabian and Thomas Flatt argued in their Nature Education review, is that evolution never really tried. Not because it couldn’t, but because it had no reason to. And understanding why requires a short trip into the logic of natural selection itself.Evolution Might Have Been ‘Blind’ To Human AgingLife in the natural world was short, dangerous and unforgiving for most of evolutionary history. Predators, starvation, infection, accident were daily realities for our ancestors. In such an environment, most individuals died young. Deat...