Your article reminded me that taking a bird’s song and transposing it down four octaves makes it sound like a whale’s song. The opposite is also true. To hear this, go to

Todd Barton
Ashland, Ore

The article would imply that the only anomaly to the theory that mass equates to longevity is that large-dog breeds live shorter lives than small ones do. I would suggest that there are many more discrepancies. For example, humans outlive elephants, horses, and cows, and tortoises outliving humans. And amoebas outlive us all.

McClellan Blair
Indiana, Pa

This is tremendously interesting. The scaling law is evidently expressible in a single formula. Why not present it?

Patrick J. Roache
Socorro, N.M.

Here’s the equation , I = i0 M 3/4 e –E/kT . I is an individual’s metabolic rate , i0 is a normalization constant , M is mass , E is the activation energy , k is Boltzmann’s constant, and T is body temperature in kelvins .—E. Klarreich

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