secure a uniform expression of the basal metabolism findings on different animals species are utterly futile…. [N]o unifying principle in metabolism has been found to exist.

It takes an unusual scientist to collect this much information and not see any trends in it—most, using the human gift for spotting patterns, will begin joining the dots as soon as they have two data points. And as Kleiber pointed out, measuring the metabolic rate of one animal is a unification, a summing-up of the pooled activities of millions of cells—does that make it a meaningless quantity? “If this is the way Benedict feels,” he retorted, “one cannot help but wonder how he ever became interested in conducting a respiration trial.” The dispute between lumpers such as Kleiber and splitters such as Benedict about how we should compare different measurements of metabolic rate and what such comparisons reveal continues to this day. But both Kleiber and Benedict agreed that the surface law could no longer stand.

To misquote Thomas Huxley, the surface law was a beautiful theory destroyed by beautiful facts. But Rubner’s law was one of those wrong ideas that, because of all the thought, arguments, and experiments it stimulated, proved a lot more useful and influential than many a correct notion. In Rubner’s time, biological knowledge, with the giant exception of Darwin’s theory, was a pile of facts. Biologists accumulated information about the living world, but there was little attempt to put it into context, to see if any larger structures emerged from the mass of details. In the years between the two world wars, the debate on whether the surface law held or not was one of the most active in biology. Without Rubner’s search for laws of metabolism, Kleiber might never have been stimulated to find general trends in the data. Even today, biological principles that make firm predictions across a wide range of species are extremely rare. Kleiber’s rule is one of the few examples and one of the most precise. If Bergmann’s rule was like Kleiber’s, rather than being a general trend with many exceptions, we could point to a spot on the map and say with reasonable confidence what size animals lived there.

Yet Kleiber’s discovery only made things more puzzling. To believe that metabolic rate corresponds to the relationship between body mass and surface area, or mass raised to the power of 2/3, is intuitively



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