Why does human life expectancy approach the radius of a certain number or group? Why can’t some humans live past 200 years? Why do humans not die at like 30?
In: Biology
ONLY 70!? Dude I’m amazed it’s even that high. Considering how randomly death seems to be. Dad’s an EMT. Sees lots of people of all ages die. Sorry to be macabre, and I hope I didn’t just send anyone into an existential panic, just pretty stoked I made it to 26.
Humans used to die around thirty, and then modern medicine helped us understand “germs” and how to defeat them. Diets and environmental changes helped, too.
Diets and aging are now why people wear out in their eighties and nineties. Many die in their sixties and seventies, and before, because of diet and environmental impacts shortening the inevitable.
Even with “replacement parts,” life isn’t usually significantly increased in the extreme cases. Usually a handful of years, often because of the surgeries and medicine that goes with them.
George Carlin pointed out that you can eat healthy and exercise, but you’ll die anyway. We haven’t discovered the magic balance, but it seems that at least for now, the decline that starts in your thirties or forties ends within sixty years. Still a good run.
To answer your question in evolutionary terms, the aging process begins at a point where optimal reproduction would have taken place and one’s children would be nearing/have reached the age for reproduction, combined with which age we were likely to have been killed off by predators, disease, or other aspects of our environment that our body couldn’t control. After this, our genes become effectively ‘blind to selection’ and so stop working properly, leading to reduced maintenance and upkeep of our body.
Put another way, our bodies take about 15 years to mature, we then have a few years where we’d have been having children as ancient humans. We then have to look after our children for another 15 or so years until they can have their own. This timeline is partly determined by how fast we can grow (biologically and according to resources) and by when we would’ve died by other causes. At a point where there would be more children to look after the next generation than there would be parents (now grandparents), natural selection on upkeep of our bodies starts to break down and become weaker as our kids and theirs are now in the limelight. As a result, we begin aging in our 30’s (this is how long it takes us to grow and reproduce, and about the time by which the majority of our generation would’ve been killed by something else).
Of course, its not an outright collapse, our bodies still try to keep themselves in good shape, but more and more genes start malfunctioning. We’ve also become really good at stopping the environment from killing us and providing ourselves with optimal nutritional resources. These all allow our bodies to often hold out for a good few years more
Eventually, your body’s structure starts coming apart beyond repair and your cells start to grow back wrong.
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