Red herrings and rotten fish

A longstanding problem in biology has been the origin of pervasive quarter-power allometric scaling laws that relate many characteristics of organisms to body mass (M) across the entire spectrum of life from molecules and microbes to ecosystems and mammals. In particular, whole-organism metabolic rate, B=aM^b, where a is a taxon-dependent normalisation constant and b is approximately equal to 3/4 for both animals and plants. Recently Darveau et al. (hereafter referred to as DSAH) proposed a "multiple-causes model" for B as "the sum of multiple contributors to metabolism", B_i, which were assumed to scale as M^(b_i). They obtained for average values of b: 0.78 for the basal rate and 0.86 for the maximally active rate. In this note we show that DSAH contains serious technical, theoretical and conceptual errors, including misrepresentations of published data and of our previous work. We also show that, within experimental error, there is no empirical evidence for an increase in b during aerobic activity as suggested by DSAH. Moreover, since DSAH consider only metabolic rates of mammals and make no attempt to explain why metabolic rates for other taxa and many other attributes in diverse organisms also scale with quarter-powers (including most of their input data), their formulation is hardly the "unifying principle" they claim. These problems were not addressed in commentaries by Weibel and Burness.