The American journal of clinical nutritionJun 1, 1992

Why Different Species Live for Different Lengths of Time

Updated Feb 11, 2026

Abstract

Natural selection may favor shorter life spans by prioritizing reproduction over long-term cellular maintenance.

Physiological processes regulate species longevity and are influenced by evolutionary selection forces.
Aging may result from the accumulation of unrepaired cellular damage, aligning with the 'disposable soma' theory.
The genetic control of longevity could be linked to the investment in cellular maintenance systems relative to environmental risks.

Simplified

Proximate answers to questions about species longevity are to be found in the physiological processes that regulate duration of life. But what are these processes, and how are they themselves controlled? This leads to ultimate, evolutionary questions about longevity. What are the selection forces that favor one life span instead of another for a given species? To understand the evolution of life span we need also to understand the evolution of aging. A plausible hypothesis is that because of the requirement for reproduction, natural selection favors a strategy that invests fewer resources in maintenance of somatic cells and tissues than are necessary for indefinite survival. This "disposable soma" theory predicts that aging is due to the accumulation of unrepaired somatic defects and the primary genetic control of longevity operates through selection to raise or lower the investment in basic cellular maintenance systems in relation to the level of environmental hazard.

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