The Quest for Immortality: Science at the Frontiers of Aging

The Quest for Immortality: Science at the Frontiers of Aging, by S. Jay Olshansky and Bruce A. Carries (W. W. Norton, 2001; $25.95)

Living to a very advanced age is unlikely, the authors argue. But are they right?

Although the dangers of basing predictions of the future on short-term statistical trends are well known, they're sometimes conveniently forgotten. Johns Hopkins University biostatistician Raymond Pearl, one of the grand characters of twentieth-century science, spent much of his career examining the growth trajectories of fruit fly and mouse populations to determine whether there was a universal law of mortality--the logistic curve. Logistic population growth proceeds rapidly at first, then gradually slows to a stop as it comes up against a biological limit. Invoicing this "law" in the early 1920s, Pearl predicted that the world's population would reach its limit of 2 billion in the year 2026. In fact, it reached the 6 billion mark in 1999.

Similarly, in their book The Quest for Immortality: Science at the Frontiers of Aging, demographers S. Jay Olshansky and Bruce A. Carnes cite another statistical law of mortality, the Gompertz function, which states that the chance of dying doubles every seven or so years after puberty. The authors project that maximum human life expectancy (currently between seventy-five and eighty years in the countries with the best health status) will not exceed eighty-five years anytime soon. They also think we should be glad it won't, because society might collapse under the collective expense of supporting the decrepit and demented elderly. To support this view, and to expose the long and continuing history of human folly in the pursuit of immortality, they have written a delightfully accessible, evolutionarily sensible, and often highly personal book on the history of prospects for human longevity.

Some demographers, believing that the Gompertz pattern has no discernible biological underpinnings, vehemently disagree with Olshansky and Carnes and assert that babies born today can expect to live as long as 100 years. Underlying these contending projections are very different visions of biology and the future of humanity. The Carnes-Olshansky vision is that our bodies are like race cars, exquisitely designed to perform well for a certain time but likely to collapse as the parts--engineered to last only so long--give out one by one at an accelerating rate. So many things go wrong late in life that improved success in treating individual problems doesn't affect average survival all that much. Carnes and Olshansky have calculated, for instance, that eliminating all cancers (responsible for about 25 percent of all U.S. deaths) would increase life expectancy by only about three years. In giving as clear an explanation of the relation between evolution and aging as I have ever come across, they assert the necessity of a collective collapse of parts. They also make an excellent case that given the current state of medical technology, the assumptions necessary to project a 100-year life expectancy defy biological rationality.

But the authors' concentration on the average age at which individuals die can be misleading. Life expectancy anywhere in the ,world before the past couple of centuries probably never exceeded twenty-five or thirty years. This doesn't mean that an adult was considered elderly at forty or that extreme ages weren't reached--only that infant mortality, which has a disproportionate effect on life expectancy, was very high. The ancient Egyptians, for instance, understood old age in terms that are easily recognizable today. One pharaoh, Ramses II, probably lived into his nineties.

Aging is not a modern phenomenon. What is modern is the likelihood of living to a very old age. The probability in the United States of any given person's reaching eighty is now double what it was in 1940, but this means that more people than ever before will be leading lives of chronic disability. What we are now adding to our lives is what these authors call manufactured time--that is, life purchased by medical intervention but not necessarily high-quality life. Yet need it be so?

Prolongevists believe that aging and death can be modified right now. All we need to do is swallow supplements, follow a special dietary plan, inject hormones, use certain relaxation techniques. Such beliefs can be traced back at least to early Taoism, in the third century B.C., and their historical development is nicely documented here. One thing common among antiaging therapies, then and now, is the lack of any evidence that they work. My current favorite in this vein (so to speak) is the injection of human growth hormone, the virtues of which have been promoted by Hollywood celebrities and "medical experts." There does exist firm documentation that this hormone can increase muscle mass and decrease body fat (as do exercise and anabolic steroids). The popularity of such injections is particularly ironic, however, given that convincing evidence has accumulated over the past three to four years that in mice, at least, increased growth-hormone levels lead to a shorter life.