American Scientist

To the Editors:

I found the article "The Evolutionary Truth About Living Fossils" by Alexander Werth and William Shear (November–December) informative. On page 440, the authors mention “the role that stochastic contingencies play in evolutionary history” and state that “survival of a living fossil [may depend on] chance events in history.”

If it is correct that evolution proceeds because a few of the many random mutations occurring provide competitive advantages for organisms in certain environments, then it seems not only possible but likely that a few of the species that have arisen on Earth would persist relatively unchanged over long time scales.

Maybe there is an opportunity for a statistician to be tasked with an analysis of species longevity. I suspect that the existence of living fossils—the black swans of evolution—would not turn out to be surprising at all.

Stephen L. Brown
Alameda, CA

Drs. Werth and Shear reply:

Many paleontologists, particularly the late Jack Sepkoski, have performed statistical analyses on species turnover and longevity. These studies have led to important findings, including the detection of patterns of mass extinction events in the fossil record. Other statistical studies include investigation of what percentage of dinosaur species or genera have been discovered.