The Panda's Thumb

"The Panda's Thumb" is a famous essay by Stephen Jay Gould that uses the panda's wrist bone as a metaphor to explain how natural selection involves adaptation through modifying existing structures. The panda's "thumb" isn't a true thumb but a specialized wrist bone that functions like one, allowing pandas to grasp bamboo. Gould argues this showcases how evolution repurposes available parts rather than designing perfect features—that many features are "pandas' thumbs," functional but not ideal. It highlights the creativity of natural selection in shaping structures to suit specific needs through gradual modifications.