The panda's 'thumb' isn't a finger at all

Giant pandas grip bamboo using a sixth digit that looks and works like a thumb — but it's actually an enlarged wrist bone, the radial sesamoid, not a true finger. Stephen Jay Gould used it as a textbook example of evolution's clumsy tinkering: not the elegant design an engineer would choose, but a workable fix built from whatever was already there.

— Stephen Jay Gould, The Panda's Thumb — W. W. Norton, 1980
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