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Life is destructive. Our environment and our internal functions all wear and tear at our body over time. Evolutionarily speaking, natural selection rewards those who can survive such hardship. So why don’t we live forever—why age at all?
There have been numerous attempts to understand how and why we age—as recently as 1990, the biologist Zhores Medvedev tallied more than 300 possible hypotheses. But according to Steven Austad, a biogerontologist at the University of Alabama at Birmingham, one explanation has risen to the top: “Reproduction is the name of the game. Basically, we age because it’s not in nature’s best interest to perfectly repair our bodies. The main thing is to keep us reproductive as long as possible, and then let our bodies deteriorate.”
The rate of aging in humans and other mammals, Austad says, might be determined by how quickly we have to reproduce before we’re killed off by other factors. In general, the smaller the animal and the more hostile its environment, the shorter it lives. A field mouse, for example, must breed before a hawk snatches it up, and so its organs and immune system don’t need to last 50 years. On the flip side, elephants have few threats, so their bodies can keep going for decades. “In an evolutionary sense,” says Austad, “that is the timekeeper.”
Read full, original post: Why do we age?