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.
"We see ourselves on the cusp of the second longevity revolution," agrees Jay Olshansky, a demographer at the University of Chicago and the author of The Quest for Immortality (2001). "Scientists are on the verge of discovering major secrets of aging." The first longevity revolution occurred in the early 20th century, as infant mortality declined and infectious diseases were conquered; as a result, more young people now enjoy the opportunity to become old. The next longevity revolution, by contrast, will actually postpone old age.
Of the two researchers, Olshansky can be considered the pessimist. He bet Austad $500 million that there will no 150-year-old person alive and in fairly good shape in 2150. The bet was set up as a trust fund endowed by $150 from each scientist. Given the math behind compound interest, the winner's heirs will get the $500 million payout on January 1, 2150.
Love and Death
Woody Allen might appreciate the science of longevity as well as the results. Sex and death, it turns out, are inextricably intertwined. "It doesn't pay to have a body that will last forever," notes Austad. "Evolution only cares about reproduction." Every body harbors a line of immortal cells: the germ cells that produce eggs and sperm. Germ cells migrate from body to body down the millennia, disposing of their worn-out carriers as they move on. Once your ovaries or testes are done with you, they couldn't care less whether you live.
Here, then, is the definitive an-swer to the eternal question: Which came first, the chicken or the egg? The egg did. A chicken is merely an egg's way of making more eggs.
In the case of human beings, evolution has selected for a set of genes that keep our bodies in pretty good shape long enough to mature sexually, produce progeny, and raise those progeny to sexual maturity. Time elapsed: about 40 years. The evolutionary insight here is that if a body invests a lot of energy in repairing itself, it will reduce the amount it can devote to reproduction. That may be good for individual bodies, but your germ cells have no interest in keeping you forever young.
The UCLA biologist Michael Rose firmly established the evolutionary connection between sex and death by breeding fruit flies. Rose selected only those flies that reproduced late in life and bred them with one another. The longer it took the insects to reproduce, the longer they lived. Rose now has flies that live 130 days instead of the usual 40.
The connection was further bolstered this January by Cynthia Kenyon, a biologist at the University of California at San Francisco. Kenyon reported that she could double the life spans of nematode worms by removing their germline stem cells -- the cells that produce eggs and sperm. Then there's Lawrence Donehower's recent research at Baylor Medical College. Donehower has found that the genes that are helpful in guaranteeing a robust youth are harmful in the long run. The tumor-suppressing p53 gene keeps us from developing cancers in early life, but at the cost of stimulating our immune systems to destroy over time the reserve of rapidly dividing stem cells that replenish our tissues. As our stem cells are killed off, our tissues deteriorate. The result of this "antagonistic pleiotropy" is aging.
Another example of antagonistic pleiotropy was discovered by the biologist Leonard Hayflick in 1961. Hayflick, now at U.C. San Francisco, found that human cells in vitro would divide only 50 to 80 times, then stop. For a while, some researchers thought this "Hayflick limit" might be the key to aging. What it appears to be is an evolved mechanism to prevent cancer. Cancer is the uncontrolled proliferation of cells, and as cells divide they often accumulate errors that predispose them toward becoming cancerous. If there is a limit on the number of times a cell can divide, such a limit prevents cells from eventually mutating into cancer cells.