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No. 59: Sep-Oct 1988

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Claims of a 26-million-year periodicity in biological extinctions have been given wide publicity recently. One theory has it that periodic comet showers have created this regular pulse beat in the history of life. A recent issue of Science presents the results of an analysis of the ups and downs of 20,000 marine genera -- that is, percent extinctions over a period of 600 million years, as revealed by the fossil record. The graph of ten groups of 1000 genera shows at least two things: (1) strong hints of periodicity; and (2) suggestions that extinctions, whatever they really are, "cut across functional, physiological, and ecological lines." The plotters of these graphs, D. Raup and G. Boyajian, claim that whatever the mechanism, "major pulses of extinction result from geographically pervasive environmental disturbances." What besides powerful, external physical forces (read "comets and asteroids") could affect such wide ranges of marine organisms? (Lewin, Roger; "Pattern and Process in Extinctions," Science, 241:26, 1988.) Comment. This all sounds so reasonable that one must wonder why it is given space in Science Frontier. The reason is that we have a suspicion that it is all too easy, too simplistic. Could something more subtle be at work? After all, we really know next to nothing about the real workings of life-as-a-whole, its ups and downs. It is so easy to say that a group of organisms was done in by a temperature change or the fall of acid rain brought on by the impact of an asteroid. We always look for external forces, whereas the real cause of "crises" in the history of life may be intrinsic to life itself.

With a tip of the hat to the Gaia hypothesis, let us think of life-as-a-whole as a most complex, interlinked system. What might be the dynamics of such a megasystem? From the mathematical point of view, many of the processes involved, as life copes with the environment, are doubtless nonlinear, which means that chaotic conditions may sometimes prevail. In fact, the graphs presented below could have been taken right out of a book on chaotic systems. Life's extinctions and explosions might have no connection to asteroids, Ice Ages, or global volcanism. If something as simple as a spherical pendulum can lapse into chaotic motion, life-as-a-whole should show occasional wild behavior, too. Take our planet's weather as another example. Idealists once thought that given enough observations and computer power, weather could be predicted. But, alas, our atmosphere has also turned out to be a chaotic system, and long-term predictions are next to impossible. So, too, with life and its development. Those extinction-explosion plots may be just the paleontological expressions of a chaotic system.

Percentage extinction vs geological time

From Science Frontiers #59, SEP-OCT 1988. 1988-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987