OLD DO MAMMALS GET?
around the globe, people are living longer than their ancestors did.
In the U.S. this means the entire age structure of our population is
shifting. Healthier diets and more exercise are partly responsible for
our increased longevity, and modern medicine certainly helps keep more
people alive for a longer time.
no matter what we do, old age finally catches up with us. Even the healthiest,
most active people eventually show signs of senility.
do not fully understand the aging process, and National Institutes of
Health funding for medical research on the phenomenon of aging in humans
is mostly reserved for studies conducted on the usual laboratory animals:
white rats, white mice, rhesus monkeys, chimpanzees, fruit flies. I
have a suggestion for NIH: Channel more money for studies on aging ecologists
doing research on senescence or the absence thereof in
various animals. These study subjects are not the typical laboratory
specimens, and none have the physiological similarities to humans that
rats, mice and primates do.
have traits that might provide researchers with a better understanding
of the process of aging.
albatrosses apparently live for more than 50 years, maybe even a hundred,
yet do not show the typical signs of senescence so common among humans.
A female albatross begins laying about one egg a year at the age of
10 and continues to do so. Presumably, a 75-year-old albatross is as
reproductively fit as a youngster of 45 or 50, showing no signs of reproductive
failure. Clearly, the albatross holds some secrets we might like to
know more about.
are another group with unusual aging traits. Most spiders live a couple
of years, not such a surprising feat, but some tarantulas have been
known to live for 35 years. One reason tarantulas may be a useful research
tool is that the males and females differ considerably in their longevity
patterns. Upon reaching maturity, the female tarantula continues to
molt, grow and reproduce. The male on the other hand, upon reaching
spider manhood at 10 years of age, mates once or twice and then dies
within a year or two. In the human population, females live slightly
longer than males. The dramatic difference in mortality rates of the
sexes in tarantulas offers opportunity to identify a specific cause
of the consistently earlier death of males. Perhaps a lesson for humans
possums could provide useful information toward understanding senescence
and some of the associated problems that accompany old age because of
their relatively short lifespans, which average less than 2 years. A
3-year-old possum teetering on the edge is likely to have cataracts,
reproductive senility and other signs of aging found in humans. The
oldest known possum lived for 6 years and 7 months in the Little Rock
Longevity of Mammals in Captivity by Richard Weigl is a
remarkable compilation of all of the documented oldest recorded ages
of the worlds mammals. Most live longer in captivity than in the
wild, offering researchers the opportunity to examine the aging process
in long-lived individuals. Many chimpanzees have surpassed the half
century mark, as have several elephants, some living to be more than
60. Great apes like gorillas and orangutans often live into their 50s.
one of the oldest documented ages for a mammal, other than humans, belongs
to a Florida manatee born in the Miami Seaquarium in 1948. It died this
year at age 69! Not only that but the manatee did not die of
old age but in an accident. Research on these, and many other species,
might be able to tell us something about our own aging processes.
as we wait for medical research to add a few more years on to our lives,
we should heed the words of George Bernard Shaw: "We don't stop
playing because we grow old; we grow old because we stop playing."
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