Between 543 and 538 million years ago, something remarkable happened. After hundreds of millions of years of gradual and painstaking evolution, suddenly the process exploded into life. For the first time animals evolved hard external parts. For the first time there was evidence of active predation, with both hunters and hunted rapidly developing both armaments and defences. And in this short space of time -- the blink of an eye, in geological terms -- the number of different classifications of animals, or phyla, mushroomed from 3 to 38, the number we still have today. The 'when' and the 'what' of this extraordinary event, known as the 'Cambrian Explosion', have been known for some years and were made famous in Stephen Jay Gould's bestselling book WONDERFUL LIFE. What has until now been speculation is the 'why'. Andrew Parker's astounding explanation, which is becoming increasingly influential and accepted, is fully explored and described in this groundbreaking book.