A young raven in British Columbia was filmed repeatedly sliding down a snow-covered roof on its back, climbing back up, and sliding down again. It had no nutritional incentive. No predator was being evaded. No skill was being rehearsed for later survival advantage, unless “sliding down a roof on your back” is more useful in the wild than ornithologists have realized. The raven was playing.
This is the thing about play that makes strict functionalists uncomfortable: it resists explanation in terms of purpose. You can tell a story about how play serves development — how lion cubs practice hunting, how rough-and-tumble play teaches young mammals to calibrate force — and those stories are true as far as they go. But they don’t go far enough. They can’t explain the raven on the roof. They can’t explain octopuses squirting water at empty bottles to watch them spin, or dolphins swimming through their own bubble rings, or crows dropping sticks from great heights and catching them in midair. These behaviors are metabolically expensive and they produce nothing. Except, apparently, something worth doing.
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