Coloured Spots v. Iridescence
- Improbable Destinies: How Predictable Is Evolution? by Jonathan Losos
Allen Lane, 364 pp, £20.00, August 2017, ISBN 978 0 241 20192 3
The issue of evolutionary inevitability was brought sharply into focus by the late Stephen Jay Gould in his book Wonderful Life (1989). Gould discussed the bizarre fossils uncovered by the Cambridge palaeontologist Simon Conway Morris in an outcrop of rock in the Canadian Rockies, known as the Burgess Shale. The shale was formed 511 million years ago, in the period when animal life was first emerging. Buried within it Conway Morris found the fossils of extraordinary creatures with no modern equivalents, animals such as Hallucigenia, a long tube with a blob of a head at one end, an upturned tail at the other, seven pairs of pointed, stilt-like legs and seven matching tubes projecting above its back. Another creature had five eyes and a long claw-tipped hose on the front of its head. The subsequent disappearance of such body plans, Gould argued, suggests that chance events shaped the direction of evolution, and that if we were to rewind the tape of life to its beginning and let it run again, it is extremely unlikely that anything like humans would come about. Conway Morris, as much a predestinarian Christian as Gould was a Marxist, strongly disagreed. In The Crucible of Creation (1998) he attacked Gould, ‘biting the hand that once fed him’ as Richard Fortey put it in his review, in a way that made ‘a shoal of piranha seem decorous’.[*] The range of evolutionary options is tightly constrained, he insisted, and wherever there is life, on earth or any other planet, human-like creatures are likely to emerge.
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