Evolutionary Theories of Ageing

The Shadow of Selection

Natural selection is strongest early in life, when survival and reproduction determine evolutionary success. As age increases, selection pressure weakens, allowing late-acting harmful effects to persist in populations. This declining selection with age is a central prediction of classical evolutionary theory. [1] [2] [3]

Mutation Accumulation

This theory proposes that harmful mutations with effects late in life accumulate because selection is too weak to remove them. Their gradual buildup contributes to age-related decline. [1] [2]

Antagonistic Pleiotropy

Some genes are beneficial early in life but harmful later. Evolution favors early-life advantages even when they carry late-life costs, such as increased disease risk or tissue exhaustion. [3] [4]

Disposable Soma

The disposable soma theory explains ageing as a trade-off in energy allocation. Organisms invest enough in maintenance to reach reproduction, but not enough to preserve the body indefinitely. [5] [6]

Summary

Evolutionary theories of ageing emphasize weakening selection, trade-offs, and late-acting damage. They explain why ageing persists even though it reduces fitness later in life. [4] [7]

References

1. Medawar, P. B. An Unsolved Problem of Biology (1952).
2. Hamilton, W. D. "The moulding of senescence by natural selection." Journal of Theoretical Biology (1966).
3. Williams, G. C. "Pleiotropy, natural selection, and the evolution of senescence." Evolution (1957).
4. Rose, M. R. Evolutionary Biology of Aging (1991).
5. Kirkwood, T. B. L. "Evolution of ageing." Nature (1977).
6. Kirkwood, T. B. L., Holliday, R. "The evolution of ageing and longevity." Proceedings of the Royal Society of London B (1979).
7. Kirkwood, T. B. L., Austad, S. N. "Why do we age?" Nature (2000).