Wednesday, July 22, 2015

David M. Raup, an Originator of the Idea that Mass Extinction Events are Periodic, Died July 9

David M. Raup, one of the founding fathers of the hypothesis that mass extinctions are periodic, died earlier this month. The New York Times ran a decent obit last week by Bruce Weber, "David M. Raup, Who Transformed Field of Paleontology, Dies at 82":
Dr. Raup’s most famous contribution to the field may have been the revelation in 1983, after a six-year study of marine organisms he conducted with J. John Sepkoski Jr., that over the last 250 million years, extinctions of species spiked at regular intervals of about 26 million years
Extinction periodicity, as it is known, enlivened the study of huge volcanic eruptions and of changes in the earth’s magnetic field that may have coincided with periods of mass extinction. It has also given rise to numerous theories regarding the history of life, including that the evolution of myriad species has been interrupted by nonterrestrial agents from the solar system or the galaxy. 
One prominent hypothesis involved an undiscovered companion to the sun — it was christened Nemesis — that every so often swung close enough to the solar system that it redirected comets toward the earth. 
Extinction periodicity remains unproven — further published analyses of the Raup-Sepkoski data have been divided on their original conclusions — and Dr. Raup was open about the fact that the data could lead him only so far. (“I believe they really are periodic,” he said of mass extinctions in a 1997 interview published online, “but I can’t prove it.”) But throughout his career, it was the questions that arose because of his work that established him as among paleontology’s most creative thinkers.
Twenty years ago, in my late twenties and into my early thirties, I was fascinated by periodic mass extinctions. I read most of the books on the subject, which at the time were numerous, including Raup's The Nemesis Affair: A Story of the Death of Dinosaurs and the Ways of Science, as well as Richard Muller's Nemesis: The Death Star.

Here is a short book review of The Nemesis Affair by Jonathan Weiner published by NYT in 1986:
THE NEMESIS AFFAIR: A Story of the Death of Dinosaurs and the Ways of Science. By David M. Raup. (Norton, $14.95.) 
In 1984 David M. Raup and his colleague Jack Sepkoski published a theory of periodic mass extinctions. Statistical analyses of fossil data suggested that the world has endured a Great Dying roughly every 26 million years. This theory added fresh fuel to the controversial hypothesis of Luis and Walter Alvarez, a physicist and geologist, and father and son, who in 1980 had suggested that the dinosaurs were killed when a big chunk of rock or ice fell from outer space. The astrophysicist Richard Muller, a protege of Luis Alvarez, soon linked both extinction theories in a long-shot, third hypothesis: the Sun has an obscure companion, Nemesis, the Death Star. Sweeping close every 26 million years, Nemesis is said to dislodge comets from their orbits and send them falling through the solar system like cannonballs. In ''The Nemesis Affair,'' Mr. Raup, Sewell L. Avery Distinguished Service Professor of Geophysical Sciences at the University of Chicago, tells how each one of these theories, and some of their rivals, was born and how they were seized on by the news media - sometimes before the theories were ready. He stresses the social side of science - the roles of collegial advice, rumor, preprints, editors, editorials, peer review and especially the news media. A hot topic short-circuits the system, he argues - for better and worse. Mr. Raup is clear, low-key and good-humored. ''The Nemesis theory,'' he says, ''may turn out to be a major step forward in our understanding of the natural world or an embarrassing period of near-insanity in scholarship.''
I was intrigued by the idea that mass extinction might be linked to magnetic reversals on the planet. I read Alvarez's book too.

Somehow I was going to link this up with E.O. Lawrence and color television. One of the hypotheses I was working on is if Lawrence's version of the technology would have taken off a decade or more before color TV's wide introduction in the middle- to late-1960s, the American cultural revolution would have happened sooner; the idea being that part of the freak-out of the 1960s was due to the introduction of color television. It was just too powerful a new medium for people to absorb at first.

Now that mass extinction is a popular topic once again, it would interesting to see how the Sixth Extinction fits in with Raup's periodicity hypothesis.

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