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Steven Austad is a biologist who discovered variation in
the aging process. While trapping female opossums to ___1___
their productivity in Venezuela, he noticed something
strange. He would catch an opossum in great condition,
only to catch her a few months later to find her riddled
with cataracts and arthritis. This led him to wonder why
the opossums aged at such a fast pace even though the
animals have the ___2___
to repair their cells and keep their bodies in good
working order. Austad searched through scientific
literature to find out why we age, and found a
hypothesis that explained it. Aging is an unavoidable
by-product of evolution; while repairing damaged cells
may let an animal live longer, it also ___3___
a lot of energy that could be used for other things,
such as maturing faster and having bigger litters. In
Venezuela, living fast and dying young was the best way
for the opossums to pass on their genes. Stalked by
jaguars, they were likely to be killed anyway, so
staying youthful was waste of effort. If this
theory was right, opossums that enjoyed a safer life
might also enjoy a slower, longer one.
On Sapelo Island, Austad came across a ___4___
of predator-free opossums. After tagging and tracking
these opossums for the next few years, Austad discovered
that these stress-free opossums lived 25 percent longer
than their cousins in Venezuela. They also enjoyed
better health for a longer time. Austad started to
formulate an idea that would form the basis of his
research for the next 20 years. Aging is not set in
stone, it can actually ___5___
stretched and squashed as animals adapt to their
changing world. In fact, Austad and other researchers
found they could make animals live longer, either by
changing their diets or modifying their genes. |
