Goat testicle transplants. Elixirs of jade. Inhaling the breath of virgins. Injecting crushed dog gonads. Drinking radioactive waters.

These are just a few of the ways people have sought to lengthen their lives and renew their vitality. The oldest narrative to come down to us through the millennia -- the Gilgamesh saga, from ancient Sumeria -- describes a quest for immortality and perpetual youth. Enkidu, bosom buddy of the semi-divine King Gilgamesh, is killed for mocking the gods. The heartbroken king seeks the advice of Utnapishtim and his wife, the only two mortals to whom the gods have granted eternal life. Utnapishtim directs Gilgamesh to a certain waterweed that will restore his youth. Gilgamesh finds it but falls asleep, and a snake eats the weed. In the end, Gilgamesh realizes that the only immortality human beings can aspire to is making names for themselves as builders of cities.

This is, to say the least, unsatisfactory. As Woody Allen once put it, "I don't want to achieve immortality through my work. I want to achieve it through not dying." Modern biomedical researchers, in the quest for the equivalent of Gilgamesh's waterweed, have made great progress in unraveling the mystery of aging. Physical immortality may not be in the immediate offing, but the day may come when death is radically postponed, if not fully optional.

The barriers to this goal are not just biological but political. Believe it or not, some of our most influential contemporary intellectuals are opposed to the idea of long, healthy lives. "The finitude of human life is a blessing for every individual, whether he knows it or not," wrote Leon Kass, the president's favorite bioethicist, in the May 2001 issue of First Things. Francis Fukuyama warns in his new book Our Posthuman Future that young geezers will "refuse to get out of the way; not just of their children, but their grandchildren and great grandchildren."

And then there's Daniel Callahan, co-founder of the Hastings Center, the nation's leading bioethics think tank. "There is no known social good coming from the conquest of death," he declared at a March 2000 conference on aging and life extension. He added, "The worst possible way to resolve this issue is to leave it up to individual choice."

On the scientific front, though, there's good reason for optimism. "The prospects of dramatically increasing human longevity are excellent," declares Steven Austad, a biologist at the University of Idaho. "Don't expect them tomorrow, but there will be major advances within the next 50 years." Austad, author of the 1997 book Why We Age: What Science Is Discovering About the Body's Journey Through Life, expects 20- to 40-year jumps in longevity to occur later in this century.