In 1883, German physiologist Max Rubner proposed that an
animal's metabolic rate is proportional to its mass raised to
the 2/3 power. This idea was rooted in simple geometry. If one
animal is, say, twice as big as another animal in each linear
dimension, then its total volume, or mass, is 23 times as large,
but its skin surface is only 22 times as large. Since an animal
must dissipate metabolic heat through its skin, Rubner reasoned
that its metabolic rate should be proportional to its skin
surface, which works out to mass to the 2/3 power. In 1932,
however, animal scientist Max Kleiber of the University of
California, Davis looked at a broad range of data and concluded
that the correct exponent is 3/4, not 2/3. In subsequent
decades, biologists have found that the 3/4-power law appears to
hold sway from microbes to whales, creatures of sizes ranging
over a mind-boggling 21 orders of magnitude. … Rubner was on the
right track in comparing surface area with volume, but that an
animal's metabolic rate is determ