The Panda’s Thumb

from the diary: “Saturday 3/15/86

“Finished Stephen Jay Gould’s Panda’s Thumb.”

I loved Panda’s Thumb. Over the years I’ve read each of Gould’s collections of essays not long after they came out.

The thumb of the panda is not an articulated digit. It’s a wristbone that juts out. It’s rigid. But it makes the panda’s paw that much handier. The panda’s ancestors were meat eaters. At some point the panda switched to its famous bamboo diet. And the pandas who could most easily manipulate a bamboo pole in order to strip it of its tasty leaves were fatter and handsomer than those who were all clumsy-pawed. Fatter and handsomer means more kids (which, in panda terms, must mean two in a decade rather than one). Over time all the kids had handy paws. But why not a real thumb? Why a jury-rig thumb? The articulatable digits had all been spoken for. A jutting wristbone was an easier fix than reversing the fusing of the digits in that hefty bear paw. Nature/natural selection prefers the easier fix.

(OK, these guys say the thumb is not rigid; plus which they have pictures. And here is an interesting sequel of sorts, that includes a link to a pdf of Gould’s original panda’s thumb essay.)