In the Blink of an Eye by Andrew Parker, Free Press, 拢18.99, ISBN 0743219805 Reviewed by Douglas Palmer
THE Cambrian explosion, sometimes called the 鈥渂ig bang鈥� in animal evolution, was 鈥減erhaps the most dramatic event in the history of life鈥�, says Andrew Parker, when 鈥渁ll the major animal groups found today evolved鈥�. He tries to pin down its cause in his book In the Blink of an Eye. It happened 鈥減recisely 543 million years ago鈥�. According to Parker, 鈥�544 million years ago there were鈥hree animal phyla鈥ut at 538 million years ago there were 38.鈥� Sounds dramatic alright, but Parker will have more than a few palaeontologists choking on their cornflakes.
Parker is an Australian-born zoologist now at the University of Oxford, where he has been investigating the evolution of coloration and light reception in living sea creatures. He has become fascinated and increasingly embroiled in a long-running debate about the nature of the Cambrian explosion. His explanation is that the light on the road to the evolutionary Damascus was the sudden appearance of the eye.
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This visionary event is indeed recorded by the appearance of fossil trilobites close to the beginning of the Cambrian. The record of the major increase in diversity, however, is linked to the appearance of the Chengjiang fossil biota of about 515 million years ago. How many millions of years can a big bang last before it becomes a prolonged, if energetic, fizzle?
Parker argues that eye evolution caused the explosion because it was linked to the evolution of actively swimming predators and a rapid development of the ensuing arms race. The evidence shows that fossilised armour plating bears the scars of conflict. That the Cambrian 鈥渆xplosion鈥� had an ecological basis is widely accepted, but the academic parliament will be divided: 鈥渆yes鈥� right, 鈥渘os鈥� left, but I think we still don鈥檛 have the result of the division.