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How Long Can We Live? : We May Be Able to Push Our Life Spans Past Our 80s, but Would We Want to, Unless We Could Also Guarantee the Quality of Those Years? : Biologists Caleb Finch and Michael Rose are tackling the issue from different approaches, but both agree that aging can be postponed.

December 04, 1990|SHARI ROAN | TIMES HEALTH WRITER

Life does not have to end at 85, or 100, or even 120. So says a small but elite group of researchers exploring the possibility of increasing our life span.

"Aging is no longer regarded as a monolith; an unmovable frontier," says USC biologist Caleb E. Finch. Finch believes in using common good-health practices like eating right and exercising to control our environment and exploit the "plasticity" of life span.

"We probably, with existing technology, don't have to invent anything new to get to the heart of biological aging," he says. "I'm highly optimistic."

Michael Rose of UC Irvine suggests the key to longer life lies in evolution and is studying a link between delayed reproduction and increased longevity in fruit flies.

"We have all the basic science to postpone human aging right now," he says. "And I have a plan for doing it."

The two researchers are old friends and colleagues who take very different approaches to the problem but reach the same conclusion:

Life expectancy is not capped by some unyielding force.

Their beliefs ignore the traditional consensus among researchers that life expectancy is controlled by an inevitable breakdown of body processes. In a recent article in Science magazine, scientists suggest that natural degeneration caps our life span at about 85 years.

In fact, no one knows how to dramatically increase how long we can live. But in recent years, scientists have moved away from believing that aging is the result of a single gene that goes awry late in life.

Instead, they believe theories that suggest aging is the result of many processes, linked to genes and the environment, working to wear down the body. These newer theories raise the possibility of intervening to stop the chain of events that cause aging.

"It's now a question of whether people want to (pursue) this," Rose says.

Finch and Rose have produced some of the most powerful evidence of the potential to extend the life span. And each has a new book that makes a strong case for going after the fountain of youth.

Rose, an evolutionary biologist, is the leading proponent of a theory of aging based on evolution.

With a youthful face and punk hair, Rose looks as if he would be more at home on MTV than on the seventh floor of the UCI Engineering Building. But he has turned many skeptics into supporters in recent years.

The purpose of his book, "Evolutionary Biology of Aging" (1991, Oxford University Press), "is to argue that aging can now be regarded as a problem that is well on its way toward a scientific solution."

Scientists are more interested than ever in the longevity question because of recent success by Rose and others with experiments that have shown the life span can be extended in lab animals.

In experiments on fruit flies, worms and mice, it's "very easy for us to . . . postpone aging so that life span can be doubled or the pattern of deterioration with aging can be vastly slower," Rose says.

The experiments focus on finding which genes are important to the aging process in order to manipulate them.

Rose, for instance, is studying whether aging can be influenced by manipulating the process of natural selection--the force of nature that favors the young (who can reproduce) far more than the old.

Rose says his studies show that the age at which a species reaches maturity--and is able to reproduce--is linked to the onset of aging. That means that the way to keep natural selection working later in life is to postpone reproduction until a relatively advanced age.

Over the past 15 years, Rose has bred fruit flies at later and later ages--increasing their life span by 80%. He is selecting as parents only older flies that can pass on longevity genes.

Scientists have delayed reproduction and increased life span in other species, and are now trying to understand why the process works. They want to know which genes that affect life span are inherited or eliminated by postponing reproduction.

For the fruit fly, Rose has shown that at least 100 genes may be involved.

But the research will contribute little to the understanding of human aging, Rose says, unless the same experiments can be tried on mammals, such as mice. That is where his "plan" for expanding life span comes in.

"If we can use a mouse to postpone aging, than we will begin to find out how to do that in man," he says. Ten years of work on mice, he suggests, could probably reveal the genes, processes and cell biology involved.

"Then we can try out direct interventions to postpone aging," he says, first on mice, then on humans.

Finch also believes that plenty of evidence challenges the assumption that our life span has a limit. But he believes that study of common health practices--such as exercising and hormone treatments to reduce the risk of osteoporosis--will contribute significantly to the understanding of aging.

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