Evolutionary Biology Blogι**=7/3ψ
by Lars Witting

Back on the allometric track

Protozoa, like this Paramecium caudatum, have an allometric exponent for mass specific metabolism in-between the exponents for prokaryotes and multicellular animals, indicating a shift in the selection of mass between the three major lifeforms. Photo: (c) iStockPhoto.com

Major lifeforms like those of virus, prokaryotes, unicellular eukaryotes and multicellular animals fall in distinct size classes, with distinct allometric profiles. The natural selection of these allometric transitions with mass may thus explain the evolution of the major lifeforms.

By having no intrinsic metabolism, viruses have evolved beyond the domain of an allometric scaling between metabolism and mass. And where multicellular animals with Kleiber scaling have a negative 1/4 exponent for the allometry between mass specific metabolism and mass, the exponent is strongly positive in prokaryotes with a value around 0.84 (Delong et al., 2010). And with an apparent invariance between mass specific metabolism and mass (Makarieva et al., 2008), unicellular eukaryotes may lie on a natural selected continuum that link prokaryotes with multicellular animals.

As the metabolic allometry is changing across the major size classes, I have decided to extend the “allometries are selected by the selection of mass”-hypothesis (Witting, 1995, 1997) to explain allometric transitions between virus, prokaryotes, unicellular eukaryotes and multicellular animals. This is revealed in four forthcoming papers that will explain the four lifeforms, and much more, as a direct consequence of the natural selection of metabolism and mass.


  • DeLong, J.P., J.G. Okie, M.E. Moses, R.M. Sibly and J.H. Brown 2010. Shifts in metabolic scaling, production, and efficiency across major evolutionary transitions of life. Proceedings of the National Academy of Sciences 107:12941--12945.
  • Makarieva, A.M., V.G. Gorshkov, B.Li, S.L. Chown, P.B. Reich and V.M. Gavrilov 2008. Mean mass-specific metabolic rates are strikingly similar across life's major domains: Evidence for life's metabolic optimum. Proceedings of the National Academy of Sciences 105:16994--16999.
  • Witting, L. 1995. The body mass allometries as evolutionarily determined by the foraging of mobile organisms. Journal of Theoretical Biology 177:129--137.
  • Witting, L. 1997. A general theory of evolution. By means of selection by density dependent competitive interactions. Peregrine Publisher, Århus, 330 pp, URL http://mrLife.org.