The evolution of human longevity.

In the comparatively short history of human evolution man's lifespan has doubled, posing the question, by what means was this prolongation of life achieved. One line of thought correlates lifespan with oxygen consumption and energy generation, pointing out that small homeothersms which expend energy at a very high rate, are invariable short lived, while animals living more economically in terms of energy expenditure, like some heterotherms and large homeotherms, can attain greatly increased lifespan potentials. The correlation between lifespan and energy expenditure is generally valid, but some animals with low energy needs, notably tropical animals and some lethargic, inactive animals, do not live as long as expected on the basis of the theory. The present paper suggest that the aging process could be accelerated by hyperthermia and the longevity of some homeotherms, beside its connection with energy needs, could also be correlated with the evolution of temperature regulating mechanisms, resulting in more accurate thermal homeostasis. Man's uniquely capacious sweating mechanism, for example, may play a part in the attainment of his long life.