*Is death an evolutionary adaptation? If so, that might mean science
could eliminate it*
Posted Sept. 27, 2004
Courtesy 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." *
Front image courtesy Biotechnology Australia*
*
[Homestead] Evolution---group selection in the case of programmed aging, vs. more common individual selection---sounds reasonable,
tvoivozhd, 01/02/2005