Since no one wants to age, there is a tremendous incentive to prevent, slow down or even reverse it. But all these efforts run into the same obstacle. No one actually knows what aging is or precisely what causes it. On its face, this riddle shouldn’t exist. The universe is subject to entropy, which causes everything, including the universe itself, to run down like a child’s toy whose battery slowly runs down. Biology chimes in with the obvious fact that all higher living things grow old and die.

But reality changes depending on your viewpoint, and one viewpoint tells us that aging, especially human aging, could be a mistake. First, we need to counter the evidence that living things must grow old and die. This is more easily done than you might suppose. Here’s a thumbnail sketch of the co...