Arguments Against Disposable Soma Theory

Arguments Against

Disposable Soma Theory

Type: Non adaptive hypothesis

Definition: “Aging” has environmental or somatic and not genetic causes, and evolutionary responses to them are increasingly limited at older ages by physiological, biochemical or environmental constraints. So, in the evolutionary search of an optimal allocation of metabolic resources between somatic maintenance and reproduction, the first is sacrificed.

Theoretical arguments against the hypothesis:
This hypothesis implicitly assumes - without any proof - that the hypothesized constraints have no alternative with analogous advantages at early ages and no disadvantage at later ages.

Proposers: Kirkwood 1977; Kirkwood & Holliday 1979.

Empirical Evidence:
1) The existence of animals with negligible senescence is against the hypothesis
2) The inverse correlation observed in the wild between extrinsic mortality rate and proportion of deaths due to intrinsic mortality is against the hypothesis
3) The existence of mechanisms genetically determined and regulated limiting cell turnover and, therefore, lifespan is against the hypothesis
4) The negative relation between caloric intake and lifespan is against the hypothesis

Conclusion: The hypothesis appears clearly falsified by empirical evidence and cannot be presented as a sound plausible explanation of aging.

References:
- Kirkwood, T.B.L. (1977) Evolution of ageing. Nature 270, 301-304. [PubMed] [Google Scholar]
- Kirkwood, T.B.L. & Holliday, R. (1979) The evolution of ageing and longevity. Proc. R. Soc. Lond. B. Biol. Sci. 205, 531-546. [PubMed] [Google Scholar]