Books 



THE NEMESIS AFFAIR: 



A Story of the Death of Dinosaurs and the Ways of Science 



by David M. Raup 



W. W. Norton & Co., 212 pages, $14.95 



Reviewed by David L. Hull 



Professions Keep Themselves Well Insulated from 



outsiders by several layers of hypocrisy. Those on the 

 inside know how the profession actually functions but 

 keep this knowledge to themselves either because they 

 are too shy to speak up or because they fear the effect that 

 such revelations might have on their profession. I 

 suspect that most professionals are wise to participate 

 in this conspiracy of silence. If the general public dis- 

 covered what really was going on, there would be hell 

 to pay. 



David Raup thinks that science is an exception. 

 Yes, scientists are as hypocritical about science as 

 doctors are about the medical profession or professors are 

 about teaching, but Raup thinks that they need not be. 

 He seems confident that outsiders will value science just 

 as much once they know how it actually operates as they 

 did when they believed the Just-So Stories that are 

 usually told about it, possibly more so. He presents 

 science as being composed of very human beings who are 

 fascinated by the world in which they live, who get great 

 joy from being right and not infrequently perverse 

 pleasure in showing others to be wrong, who speculate 

 wildly and doggedly insist that sooner or later evidence 

 must be brought to bear on their speculations. But most 

 of all, this book is written to say a few good words for 

 the mavericks of science, those frequently maligned 

 scientists who challenge conventional wisdom and who 

 are so difficult to tell from the lunatic fringe. 



Raup's particular subject matter is a series of related 

 hypotheses that gained the attention of scientists in 

 various fields starting in 1980 about the mass extinctions 

 which punctuate the fossil record. In the beginning 

 Raup shared the conventional wisdom — the causes for 



David L. Hull is Professor of Philosophy at Northwestern Univer- 

 6 sivy. 



groups of organisms going extinct are extremely varied 

 and haphazard, changes in the environment, 

 competition from other species, the evolution of new 

 viruses, etc. — the sorts of causes that we see operating 

 around us all the time. Following the great 19th-century 

 geologist, Charles Lyell, geologists, paleontologists, and 

 evolutionary biologists prefer to explain phenomena 

 initially in terms of familiar causes acting at current 

 rates. Only when these causes are exhausted is a scientist 

 justified in postulating more drastic, though equally 

 naturalistic causes. 



Scientists are addicted to regularities, cycles and 

 the like. Planets do revolve around stars in ellipses, 

 organisms do go through life cycles, there are circadian 

 rhythms, but so many of the cycles which scientists have 

 postulated have turned out to be illusory that in certain 

 areas of science, periodicity is highly suspect. As regular 

 as rain some historian or other will suggest that societies 

 go through life cycles or a biologist that species rise and 

 fall as regularly as the Roman Empire or the Third Reich. 

 In the case of biological evolution, these suggestions 

 about cycles and periods are even more questionable 

 because the causes which biologists acknowledge are so 

 irregular and haphazard. 



Mass extinctions have always proved an em- 

 barrassment to evolutionary biologists. If they are as 

 abrupt and massive as they appear, then how can the 

 sorts of causes acting today at current rates explain 

 them? Conventional wisdom is that they are not as 

 abrupt as they appear. The spotty, haphazard nature of 

 the fossil record makes them look so drastic. Rates of 

 extinction vary, but the same sorts of influences are 

 responsible for extinction during slow as well as more 

 active periods. The period of rapid extinction which had 

 the most dramatic effect occurred at the boundary 

 between the Permian and Triassic Periods, about 250 

 million years ago, when up to 96 percent of the species 

 existing at the time went extinct. 



