When we get old, our eyesight and hearing start to diminish, muscles quit working, and our bodies generally deteriorate. Why can’t humans be more like redwood trees that live for hundreds of years, seemingly immune to the adverse effects of aging? If we stuck around longer, we could presumably impart wisdom on younger generations, thereby benefiting the whole species. But it's not going to happen.
One theory on why humans age, proposed by University of Arizona, is that it protects against epidemics. The greater the population density, the more vulnerable that population is to a disease wiping out much of the species. The blog Ouroboros explains the theory this way:
If I (an organism) am more susceptible than average to a given disease, and that susceptibility has a genetic component, then my closest relatives (who share most of my genes) are likelier than the general population to be susceptible as well. Therefore, my continued existence poses a risk for my progeny, because I represent one more potential host for a pathogen that might infect them – potentially killing us all and ending the line altogether.
The general human tendency, however, is to fight aging at all costs. Talking with RadioLab, geneticist George Church said that advancing technology could make the state of “totally dead” obsolete. Church believes that technology could, hypothetically, reverse engineer people to the point where they could put anyone back together at any time. Then, presumably, people could live forever.
Not pursuing technology that would allow humans to live forever would be “immoral,” according to Cambridge researcher Aubrey de Grey, speaking at TED. According to de Grey, aging is a disease that should be cured for the sake of future generations.
The problem with trying to live forever is not that it would be “crushingly boring” or that “dictators would rule forever” or the other straw man arguments that de Grey throws out. Instead, the problem is the hubris inherent in the quest. People age for a reason, whether or not we understand that reason just yet.