Issue Date: Dec 31, 1992
EVERY living thing was born at some time and must die, sooner or later. True, but the traditional assumption is that animals in the wild never live long enough to grow old. And, while old age is a "natural" cause of death for human beings, animals die earlier of "unnatural" causes.
However, animals kept under laboratory conditions are known to die of old age. To distinguish between longevity in artifical conditions and in nature, the terms "physiological life span" (for the former) and "ecological life span" (for the latter) are often used.