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.