Why We Age

Why we age as we do. The short sentence version! Life uses energy. Life persists across time by reproduction. Genes are what control and direct how a living organism can use energy and reproduce. (Don’t get snagged on genes “controlling” and “directing” – it’s just shorthand. There is no nature versus nurture tension – it’s always nature and nurture together.)
That was the history of life on earth. In people, our genes have to make a tradeoff – go for broke and burn up the energy young to enhance the chances of reproducing, or start out slowly so you’ll be around to make sure your offspring survive, thrive, and reproduce in turn? The second one sounds better, but if others go for broke and you don’t, you risk losing completely in the reproduction department. That’s the worst possible choice for your genes to make. On the other hand, if you go completely for broke but none of your offspring survive… Uh-oh. Nature demands a compromise between short-term and long-term goals. It’s caled pliotropy – partly you go for broke early (young women gain fat on their breasts and hips during peak reproductive years, it migrates to butt and thighs later) – partly you conserve (women live about 10% longer than men probably because grandmothers have a much bigger effect than grandfathers on the survival of grandchildren – even today, even in the ‘first world’ nations.)
Just to make sure you don’t underestimate how complex the tradeoff is, some of your genes do go for broke and other genes try to save up. Some of your genes actively sabotage other of your genes to get thier way.
There you have it. If you are or were agile, flexible, cheerful, and energetic when young, hey, exactly the traits that make you attractive to the opposite sex and increase your chances of reproducing. And if you are or will be cranky, stiff, and slow as a geezer, well, your great-great-grandparents’ genes made the evolutionary tradeoff and the waiter’s still bringing the bill.
SBrunning – the only running website, probably, to discuss pliotropy. (6/7)

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