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• #Thumbs up panda full

In recent decades, as popularized by Gould 4, 5, it has become a celebrated case of evolutionary adaptation to independently acquire an opposable thumb-like structure when the need arose. The false thumb of the giant panda (“panda” throughout text below unless otherwise specified) fascinated early naturalists 1– 3. This crude “thumb” suggests that the origin of the panda’s dedicated bamboo diet goes back to as early as 6–7 Ma.

#Thumbs up panda full

The latter constraint could be the main reason why the panda’s false thumb never evolved into a full digit. This morphological adaptation in panda evolution thus reflects a dual function of the radial sesamoid for both bamboo manipulation and weight distribution. However, since the late Miocene, the “thumb” has not enlarged further because it must be balanced with the constraints of weight bearing while walking in a plantigrade posture. We report the earliest enlarged radial sesamoid, already a functional opposable “thumb,” in the ancestral panda Ailurarctos from the late Miocene site of Shuitangba in Yunnan Province, China. In addition to the normal five digits in the hands of most mammals, the giant panda has a greatly enlarged wrist bone, the radial sesamoid, that acts as a sixth digit, an opposable “thumb” for manipulating bamboo. Of the many peculiarities that enable the giant panda ( Ailuropoda melanoleuca), a member of the order Carnivora, to adapt to life as a dedicated bamboo feeder, its extra “thumb” is arguably the most celebrated yet enigmatic.