In 1977 Carl Sagan published The Dragons of Eden. On the 25th anniversary of its publication, neuroscientist John Skoyles has teamed up with Sagan's son Dorion to write what can be thought of as its sequel. Like its predecessor, this work is an extended speculation on the evolution of human intelligence that attempts to explain what makes the crucial difference between our brains and those thought to be of our animal ancestors. Skoyles and Sagan assemble an array of hitherto-unconnected facts to reveal how our social evolution has endowed us with a symbol-using capacity that can override the genetically determined, physical density of the brain. They also demonstrate how the discovery that the human brain is enormously flexible changes the entire story of the evolution of culture, of perception and of man himself.