When Edmund Selous first saw a flock of starlings, he was both transfixed and baffled. The birds would ripple through the sky like a living sheet, thousands of them flying and turning as one. Their coordination was so precise that Selous, a serious biologist and a pioneer of bird-watching, could think of only one possible explanation—the starlings must be telepathic. After 30 years of observations, he published his ideas in 1931 in a book called “Thought Transference (Or What?) in Birds”.

The bit in the brackets is important.

No, starlings aren’t telepathic. Selous had fallen prey to a common assumption—that complicated behaviour must have an equally complex basis. Instead, we now know that complexity can arise from incredible simple rules.