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BBC News By Jonathan Amos in San Francisco
 Life
expectancy for humans is unlikely to reach 100 years or
beyond for quite some time to come, if ever, a US scientist
believes.
Jay
Olshansky, Public Health Professor at the University of
Illinois, at Chicago, said on current trends life expectancy
rates would not reach 100 until at least the 22nd Century
in France and the 26th Century in the United States.
This
pessimistic outlook comes as research suggests that the
lifespan of a mouse can be greatly increased by anti-oxidant
treatment.
The
same team of US researchers, based at the Buck Institute,
has already doubled the lifespan of a worm.
It believes
that one day, the same approach might help humans live longer.
However,
Olshansky's assessment, to be published in the journal Science
this week, is based on an analysis of data on death rates
and life expectancy for men and women of all ages in Japan,
France, and the United States.
Professor
Olshansky said the assessment showed that while many people
were living longer, the rise in life expectancy was slowing
down.
The
professor announced the results of the study early at the
annual meeting of the American Association for the Advancement
of Science in San Francisco.
Next
leap
The
oldest person ever to live, according to documented records,
was Frenchwoman Jeanne Calment, who died aged 122 in 1997.
But Professor Jay Olshansky said the majority of people
were unlikely to live beyond 85 because their bodies would
simply wear out.
"The
human body was not designed for long-term use," he
said. "It was designed for short-term use and in effect
what we're doing is pushing these bodies beyond the end
of the warranty period for living machines.
"So
when we survive into old age, just as with automobiles and
race cars, things start to go wrong, and unless we can change
the structure of the body itself or the rate at which ageing
occurs, then inevitably things will go wrong as we push
out the envelope of human survival," he said.
Professor
Olshansky was optimistic that people would continue to live
longer but the next quantum leap in life expectancy could
only occur, he said, if "biomedical researchers can
discover how to modify the ageing process and make such
a discovery widely available to the entire population".
Evolving
age
Also
speaking to the AAAS meeting, Professor George Martin said
that the body was the major flaw in boosting longevity as
the evolutionary system had no particular interest in helping
people live past their peak productive years.
Professor
Martin, associate director of the Alzheimer Disease Research
Centre at the University School of Medicine in Seattle,
said there were thousands of genes in the human body which
could go wrong in different ways in each person.
He said
the human body could evolve its own systems for increasing
life span, but that this was unlikely to be the same for
everyone.
"The
bad news is that there are so many different things that
can go wrong as we age. These can be affected by an enormous
number of potential inborn genetic variations that can modulate
how we age," he said.
Mark
Eshdoo, director of the Buck Institute, which is carrying
out the mouse research, told BBC News: "I think all
humans and all animals have a certain natural lifespan,
but that lifespan can be often determined by their environment.
"Can
we do the same thing in humans. Yes we absolutely can."
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