In animals the onset of aging is tied to physical evolution. Each animal has evolved to a given life span that accords best with its survival. Nature does not allow gross imbalances to persist; all the species fit in to their own niche of life span and follow their own specific aging patterns.
The factors that influence the life spans of different animals are so complex and subtle that explaining how animals age is difficult – more than three hundred theories currently vie for an answer.
Aging clocks are disturbing to the imagination because they are time bombs that animals unwittingly carry around inside them, the instruments of their own destruction. Our moment of death is not determined at birth; humans defy fate by building shelters against the elements, planting crops against starvation, inventing cures for disease.
Yet the biochemical inheritance that we carry within us poses a constant threat. Like Pacific salmon, our bodies have the ability to release large doses of hormones outside our voluntary control. For example, a small, nonlethal dose of cortisol is released every time we are in a threatening situation.
Also beyond our conscious control is the effect of glucocorticoids in a host of other destructive processes: muscle wasting, diabetes, fatigue, osteoporosis, thinning of skin, redistribution of body fat, fragility of blood vessels, hypertension, fluid retention, suppression of immune function, and impaired mental function.
The above are signs of steroid poisoning, which looms as a danger if patients are kept too long on large doses of steroid medications. In situations where a person cannot terminate the stress response or act it out, his own body administers a tiny dose of steroid poisoning. The danger of repeated inappropriate stress is much greater, then, than any single catastrophic stress.
Adapted from Ageless Body, Timeless Mind, by Deepak Chopra (Three Rivers Press, 1998).