by Whit Gibbons

February 6, 2005

Americans are getting older every year--individually and collectively. The entire age structure of our population is shifting. Coupled with healthier diets and more exercise, modern medicines are keeping more people alive for a longer time. But no matter what we do, old age soon catches up. Even the healthiest, most active individuals eventually show signs of senility.

An official I once spoke with at the National Institutes of Health (NIH) said he wondered if we are just leading a legion of geriatrics to Golden Pond. Physicians can keep us alive, but scientists still do not understand the process of aging. In fact, some animals show no signs of aging, but scientists still are not sure why.

NIH research money that goes to support human medical research includes some for the study of aging phenomena in animals. But most funds are reserved for research on laboratory animals--white rats and mice, rhesus monkeys, chimpanzees, and fruit flies. Funding for a different approach might provide new insights into the aging process. Maybe NIH should channel more money for studies on aging to ecologists who work with animals that are not the typical laboratory specimens. Although none have the physiological similarities to humans that rats, mice, and primates do, all have some feature that could lead to a better understanding of the aging process and why it occurs in some animals, like humans, but not in others.

Take, for example, the albatross and other seabirds. Albatrosses apparently live for far more than 50 years, maybe even a hundred. Yet albatrosses do not show any of the typical signs of senescence so common among humans. A female albatross begins laying about one egg a year at the age of 10 years and continues to do so year after year. 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.

Spiders are another group with unusual aging capabilities. Most spiders live a couple of years, not such a surprising feat. But one group, which includes the 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 age 10 years, mates once or twice and then dies within a year or two. Human females live slightly longer than males. The dramatic difference in mortality rates of the sexes in tarantulas offers the opportunity to identify a specific cause of the consistently earlier death of males. Perhaps a lesson for humans will emerge.

Another animal that could provide useful information toward understanding senescence and some of the associated problems that accompany old age is the possum. In contrast to some spiders, sea birds, and turtles that are now known to have life spans far beyond what might be expected, possums are short-lived. An average possum has a life span of less than two years, although some captives may live longer. A doddering old possum of two and half years old is likely to have cataracts and show reproductive senility.

The advantage of the possum for studying aging phenomena is that they have a lot of babies and are easily reared in captivity. Thus, within two years the researcher has a population of old individuals who can be studied for some of the same aging characteristics experienced by humans. The advantage of the longer-lived species for aging research is that they have somehow overcome such problems. The job of the scientist is to discover how. Providing medical research funds to study unusual members of the animal world might uncover some mysteries that cannot be revealed in the traditional manner. But while we are waiting, 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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