ITHACA, N.Y. -- Virtually hairless, venerably wrinkled and very nearly blind, naked mole-rats -- those homely rodents from underground Africa -- remind some zoo-goers of little old men.
The resemblance is more than coincidence. They really are really old males -- and females, too -- biologists report in an article scheduled for November publication in the Journal of Zoology (Vol. 258, Part 3). Many naked mole-rats (Heterocephalis glaber ) in laboratory colonies in the United States and South Africa have lived more than 20 years, and some are at least 26 years old, making them by far the oldest small rodents in captivity.
That distinction won't get them birthday greetings from the president. But their species is being hailed as a perfect exemplar for the evolutionary theory of senescence (or aging), which explains why some bodies wear out before others. Senescence theory also tries to explain, for example, why gerbils live only a couple of years, humans regularly live eight to nine decades and redwood trees for millennia.
"Whatever kind of organism it is, it's going to senesce," says Paul Sherman, a professor of neurobiology and behavior at Cornell University. "Of course, good food and exercise, proper medical care and avoiding risky behaviors may extend lives a bit. But nothing we can do in our lifetimes or many more to come is likely to stop senescence." Evolutionary biologists define the term as the persistent decline in fitness components with age, due to internal physiological deterioration.
In the paper, "Extraordinary life spans of naked mole-rats," Sherman and his South African colleague Jennifer U.M. Jarvis report that laboratory mole-rats have survived nearly three decades, making their life spans about 10 times longer than other similar-size rodents. "Life spans of naked mole-rats offer strong support for evolutionary theories of aging," Sherman notes.