Big mammals have big (or slow) cells

Cells use two basic strategies to adapt to the size of the organism in which they reside, say Van Savage (Harvard Medical School, Boston, MA), Geoffrey West (Santa Fe Institute, Santa Fe, NM), and colleagues. Depending on how often they divide, comparable cells in a mouse and an elephant differ in either metabolic rate or cell volume, but usually not both.

The need for such adaptation stems from simple geometry. As body volume increases, surface area increases more slowly. So an elephant radiates and loses less energy per gram than a mouse and thus requires less replacement energy per gram. Differences in organism shape and capillary density alter the exact numbers but not the principle.

Thus, what Savage and others call the “cell is a cell is a cell” theory cannot hold. With energy consumed per unit...