In Search of Deep Time: Beyond the Fossil Record to a New History of Life
For centuries, biological scientists have been using the Linnean system of classification, organizing hierarchies of life forms by their perceived similarities and differences. In the late 20th century, some scientists have taken to using an alternative system calledcladistics, which bases taxonomic classifications on ecological relationships. Under the first system, all algae fall into a single large category, which is then subdivided into various genera and species; under the second, green algae are grouped with plants, chromophyte algae with waterborne fungi, and so forth to account for the environments in which they live. Under the first system, dogs and wolves and coyotes are separated; under the second, they are united, for, the thinking goes, similarities of behavior and provenance are more important than mere lines of evolutionary descent, which can only be guessed at.The debate over cladistics has largely been confined to seminar rooms and laboratories. Henry Gee brings it to the general public in this spirited look at how the science of paleontology, that grand tour of what Gee calls Deep Time, is conducted. Replacing old family trees with "cladograms," Gee challenges long-accepted notions about the past (for example, the classification ofArchaeopteryx, which walks like a duck and quacks like a duck but is accounted for as a dinosaur) and argues for a return to rigor in testing hypotheses. His book, although about difficult issues, is immediately accessible, and readers seeking to learn something about cladistics--which Gee believes is "a revolution in thought as profound as that of Darwinian evolution by natural selection"--are off to a fine start in these pages.--Gregory McNamee