A few months ago, when I was writing an article on cities and metabolic theory for the latest issue of Seed, I spent several frustrating hours trying to explain the underlying logic of metabolic theory. For those who don't know, metabolic theory is a set of simple equations that are capable of describing the energy consumption of practically every living organism. The question, of course, is why these equations are so universal. As far as I can tell, the answer involves fractals, the geometry of blood vessels and a smidgen of chaos theory. Needless to say, I didn't get very far with my explanation, and ended up shamefully glossing over the subject.
But Robert Krulwich, in his latest NPR piece, makes the explanation look easy. He provides a really lucid summary of this very intriguing branch of biology. Check it out.
On a somewhat related note, Hugo Chavez, the president of Venezuela, has decided that something called "the metabolic effect" [sic?] means that Venezuela should transition to a different time zone:
Moved by claims that it will help the metabolism and productivity of his fellow citizens, President Hugo Chávez said clocks would be moved forward by half an hour at the start of 2008. He announced the change on his Sunday television program, accompanied by his highest-ranking science adviser, Héctor Navarro, the minister of science and technology. "This is about the metabolic effect, where the human brain is conditioned by sunlight," Mr. Navarro said in comments reported by Venezuela's official news agency. Mr. Chávez said he was "certain" that the time change, which would be accompanied by a move to a six-hour workday, would be accepted.
A classic case of woo? Or has Chavez just confused "metabolic" with "circadian"?
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I dunno.... The explanation "Nature goes easy on larger creatures so they don't wear out too quickly" seems awfully teleological. Why wouldn't the metabolism of little critters also be selected for higher efficiency?
Maybe Krulwitch makes the explanation look easy by leaving out the hard parts that would make it a real scientific explanation.
Rosie--I'm totally a non-expert here, but I think what the theory is proposing is that ALL organisms are evolving towards the highest metabolic efficiency possible given their body mass and temperature. (A correction factor for temperature reveals that cold-blooded snakes have the same basal metabolism as equally massive mammals...hmmm, maybe a ferret or something.)
Anyway, a great piece about metabolic theory was written for PLoS a couple of years ago by science writer John Whitfield. It goes into the nitty gritty and might answer more of your questions.