Living forever is just for Hollywood. But why do humans age? We are born with a robust toolbox full of mechanisms to fight disease and injury, which we might think should arm us against stiff joints and other ailments. But as we age, the body's repair mechanisms get out of shape. In effect, our resilience to physical injury and stress declines. Theories for why people age can be divided into two categories:
1) Like other human characteristics, aging could just be a part of human genetics and is somehow beneficial.
2) In the less optimistic view, aging has no purpose and results from cellular damage that occurs over a person's lifetime.
A handful of researchers, however, think science will ultimately delay aging at least long enough to double life spans.
