"Most people attribute aging solely to wear-and-tear on individuals' bodies. We know about oxidative damage to DNA and cells, so we tend to say things like, 'He died because his heart failed.' True, that's the proximate cause of death, but it doesn't explain why a person's heart lasted much longer than a gerbil's heart. Senescence theory does: Long before a particular man or gerbil was born, natural selection had acted on the genomes of their species to cause gerbils' bodies to senesce more rapidly than humans' bodies.
"Proximate and ultimate explanations for senescence are not alternative, they are complementary," Sherman adds. "The first identifies specific physiological mechanisms whose breakdown results in senescence. The second explains how natural selection has acted to maintain or fail to maintain those mechanisms."
The Cornell researcher has studied colonies of naked mole-rats living in transparent plastic tunnel systems in his laboratory since 1979, first at the University of California-Berkeley and then in Ithaca. Jarvis has done the same for her mole-rats at the University of Cape Town. The animal-care protocols they pioneered have helped zookeepers worldwide to display the intriguing creatures for the education of the general public.
In nature, naked mole-rats are known to live at least 10 years. "We think they live longer in the laboratory than they do in the wild because they're safer here, but they're pretty safe in nature, too," Sherman says. One of the factors contributing to the evolution of longer life spans is reduced extrinsic mortality, which Sherman defines as causes of death th
Contact: Roger Segelken
Cornell University News Service