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Research Article

Sizing Up Allometric Scaling Theory

  • Van M. Savage equal contributor,

    equal contributor Contributed equally to this work with: Van M. Savage, Eric J. Deeds

    Affiliation: Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America

    X
  • Eric J. Deeds equal contributor,

    equal contributor Contributed equally to this work with: Van M. Savage, Eric J. Deeds

    Affiliation: Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America

    X
  • Walter Fontana mail

    walter@hms.harvard.edu

    Affiliation: Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America

    X
  • Published: September 12, 2008
  • DOI: 10.1371/journal.pcbi.1000171

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Seizing Up Allometric Scaling Theory

Posted by Gregorio on 22 Jan 2009 at 00:14 GMT

SDF start with the claim, in their abstract, that "Present empirical data suggest that...these scaling relationships take the form of power laws with exponents that are simple multiples of one quarter." They then go on to attempt a rescue of these same scaling relationships because of deviation with the data that suggest the earlier suggestion is mistaken, when not overstated. So far no version of quarter power scaling has been shown relevant to lifespan, despite the claims of WBE to the contrary. What has been shown is that bigger things live longer, generally. But it has also been shown that more massive rats and dogs live shorter lives than their conspecifics, and most birds live longer than either despite being smaller or, in the case of rodents, even the same size. This is the elephant in the living room of the quarter power scalers who refuse to give up their desperate hold on a key scheme for publication generation. But the biggest problem is with metabolism.

SDF claim WBE elucidated the link between metabolic rate and body mass. They did no such thing. They even failed to define what metabolic rate is, other than to claim "...it is the rate at which energy and materials are taken up from the environment,...transformed...and allocated by the organism." The idea that nutrient supply and materials are involved in metabolism detracts from the idea that metabolism is exclusively about energy, and lends itself to strategies to see metabolism in terms of blood flow. SDF do this in this paper, keeping up a tradition from WBE of inconsequence for allometric scaling incapable of deductive inference.

The unit 'calorie' is retained, in keeping with its study in terms of thermogenesis and heat lapse, the way Max Kleiber studied it in 1932. This is not the way it is studied anymore. And this is why SDF are so caught up trying to bring Kleiber closer to the data. Examination of the footnotes for papers cited reveals works in which the authors all go along with the model, and no one questions it. The same claims are repeatedly made, and the criticisms of biologists are acknowledged sometimes, but often elided or dismissed.

As first handled by WBE, Kleiber's Law was taken to be about basal metabolic rate (BMR). The claim was made that increased organism mass somehow affected BMR. This claim was never elucidated. The organism's field metabolic rate (FMR) was neglected, except for the stunning claim by Van Savage to the affect it was equal to the average BMR multiplied by the number of cells in the organism [2007, PNAS]. In this paper SDF wish to explain away the deviations of the data from the WBE model by modifications of its underlying assumptions, modification that are not threatening to the model. Savage et al., in other papers, have yet to specify how changes in mass for a multicellular organism, affect the BMR of the organism's cells. They insist the affect is there, just as WBE insist that a straight line holds the secret to the relation between metabolism and aging. Nothing is said about immortal cancer cells.

We are advised, "In final analysis, we are led to the seemingly incongruent conclusion that many of the critiques of the WBE framework are misguided and the exact predictions of the WBE model are not fully supported by empirical data." The conclusion is incongruent because SDF refuse to address those critiques, or even mention them all, preferring instead to beat a dead horse in the attempt to derive another inconsequential paper.