University of Southern California and World Science Staff
Ten years ago, Valter Longo had an inkling of a theory of aging that is now challenging the dogma of one of science's heavyweights – Charles Darwin.
From graduate school to a career as an assistant professor in the University of Southern California, Longo's ideas were questioned by peers and students alike as he explored a new way to look at aging that opposes principles set forth by Darwin in his theory of natural selection.
It has long been accepted that natural selection happens on the individual level – the better suited an organism is to its environment, the more likely it is to reproduce, forcing the species to change, or evolve, over time.
Longo's theory, in contrast, hinges on a process called "group selection," believed by most scientists to be wrong because it proposes that selection happens at the group level rather than the individual.
Longo also rejects a commonly accepted theory that aging happens by chance and that, like a car, an organism runs well until it starts to breaks down and eventually just stops working.
In research published in the Sept. 27 edition of the Journal of Cell Biology, Longo proposes that aging is programmed so that the majority of a population dies prematurely to provide nutrients for the sake of a few individuals who have acquired genetic mutations that increase their chances of reproduction.
The research is based on observations of programmed aging in baker's yeast by Longo and co-author Paola Fabrizio. Scientists use baker's yeast to study aging because the molecular pathway that regulates its longevity is similar to that in other organisms, such as mice and possibly humans, said Longo.
"Basically, it is the first demonstration, to our knowledge, that aging is programmed and altruistic," said Longo, who is a gerontologist, or a researcher who studies aging. "The organisms we have studied die long before they have to in order to provide nutrients for 'mutants' generated within their own population. Thus, billions of organisms die early so that a few better-adapted individuals can grow."
Even more striking, he said, the findings raise the possibility that the same process happens in humans, with many of us dying before we have to. "If aging is programmed in yeast, and the pathway is very similar, then isn't it possible that humans also die earlier than they have to?"
Many gerontologists have speculated that if aging is programmed in our genes, it could be "cured" more easily than if it's a simple process of gradual breakdown. If aging is a gradual breakdown, trying to undo it might be akin to futilely trying to replace part after part in an old car that's steadily collapsing. If aging is hardwired, by contrast, reversing it might be more akin to tweaking the programming in a computer.
Based partly on such considerations, more gerontologists are starting to come to the view that old age might be curable. In Sept. 2003, a straw poll held at a worldwide gerontologists' conference revealed that the majority of gerontologists present thought it not unlikely that scientists could reverse aging, at least in mice, within 20 years. The poll was conducted at a conference of the International Association of Biomedical Gerontology in Cambridge, U.K.
The idea that aging is programmed into our genes isn't new. But Longo provides a theory to back up the notion, by proposing an evolutionary reason for aging.
Longo said he realizes that his theory goes against the fundamental theories of evolution, which is why he took 10 years to publish it in a major scientific journal. He combed through scientific papers dating back to the 1870s to learn about the genesis of the theory of natural selection and speaking with prominent evolutionary biologists about his ideas.
Longo's idea of group selection has begun to gain new currency among other researchers.
Group selection is the notion that populations best adapted for survival last longer and multiply faster than other populations. This contrasts with traditional evolutionary theory, which holds that this process only works among individuals, not whole populations.
Some evolutionary theorists have been finding in recent years that only group selection can explain some otherwise puzzling problems, such as why altruism, or cooperation, evolved.
Traditional evolutionary theory can't easily explain this. According to the theory, altruists should constantly be falling behind in the race for survival since they give than they receive. Thus any "altruism genes" should have been wiped out long ago. But some researchers have found that when they construct computer models of simple evolutionary processes, some forms of altruism readily evolve -- but only as long as group selection is at work. Populations containing more altruists function more smoothly, survive longer and spread their genes faster than others.
Longo's theory applies the notion of group selection to death, which in his theory, is a form of altruism.
"We're also not saying that humans are, for sure, undergoing programmed aging." Longo said. "But, most likely, most organisms undergo programmed longevity. Life is programmed. Whether death is programmed or not is yet to be determined."
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