convergent evolution: the pandas’ thumb

By Alison Campbell 15/12/2011

 And yes, punctuation & grammar skillz, I has them :-) That apostrophe really is in the right place – read on to find out why.

The tale of the panda’s thumb is well-known, & an excellent example of how the action of natural selection can result in jury-rigged solutions to problems: a result that works, but not necessarily a perfect result. I first encountered it way back when, through reading Stephen Jay Gould’s wonderful book of the same name**.

A book which refers to the familiar black-&-white giant panda (Ailuropoda melanoleuca). I’d never really thought about it before, but of course we have 2 species of panda: the big fellas, & the much smaller red panda (Ailurus fulgens). Do they have ‘thumbs’ too?

As a post by Brian Switek shows, the answer is ‘yes; yes, they do’. And this is really interesting, as the two pandas aren’t closely related. Giant pandas are bears, while reds are more closely related to raccoons. Yet they both have modified a modified wrist bone, the radial sesamoid, that functions as a thumb and allows them to grip & manipulate bamboo – a lovely example of convergent evolution.


**The original essay, with the title The panda’s peculiar thumb’, is reproduced here.

Site Meter