Charles Darwin, who attempted to explain how human intelligence developed, extended his theory of evolution to the human brain: Like the rest of our physiology, intelligence must have evolved from simpler organisms, since all animals face the same general challenges of life. They need to find mates, food, and a path through the woods, sea, or sky—tasks that Darwin argued require problem-solving and categorizing abilities. Indeed, Darwin went so far as to suggest that earthworms are cognitive beings because, based on his close observations, they have to make judgments about the kinds of leafy matter they use to block their tunnels. He hadn’t expected to find thinking invertebrates and remarked that the hint of earthworm intelligence “has surprised me more than anything else in regard to worms.”

Still, we remain the inventive species. No other animal has built skyscrapers, written sonnets, or made a computer. Yet animal researchers say that creativity, like other forms of intelligence, did not simply spring from nothingness. It, too, has evolved.

“Sometimes the human cognitive psychologists can be so fixed on their definitions that they forget how fabulous these animal discoveries are,” said Clive Wynne of the University of Florida, who has studied cognition in pigeons and marsupials. “We’re glimpsing intelligence throughout the animal kingdom, which is what we should expect. It’s a bush, not a single-trunk tree with a line leading only to us.” Some of the branches on that bush have led to such degrees of intelligence that we should blush for ever having thought any animal a mere machine.