DIVERSITY IN THE FOSSIL RECORD AND STEPHEN JAY GOULD

Stephen Jay Gould consistently cited diversity and diversity change revealed by the fossil record as a major touchstone for his career-long advocacy that paleontology had a role of the same stature as neontology in understanding evolution. He argued for a hierarchical view of evolutionary theory with genetic, cellular, organismic, and demeic levels (ending with speciation) in the province of microevolution, but with differential success of species, documented by paleontological patterns involving diversity, lying in the realm of macroevolution. Steve was involved in many pioneering studies related to change in diversity, including punctuated equilibrium, analysis of clade shape, trends produced by change in variance, and the contrast between taxonomic diversity and morphological disparity. He cited these and the role of mass extinction among the contributions of paleontology that documented a hierarchical structure to the history of life. A critical change in Steve Gould’s intellectual evolution involved diversity studies. His early analytical work and work he did with David Raup, Tom Schopf, and Dan Simberloff, in which they developed a series of computer models of evolutionary patterns, led to Steve’s 1980 suggestion that paleobiology might be developing as a rule-based “nomothetic evolutionary discipline.” However, the growth of attention to mass extinctions in the 1980s, especially the dramatic bolide-related end-Cretaceous event, plus his view of the separation of punctuated equilibrium and species selection from the operation of organismic natural selection, led Steve to develop a multi-tier view of evolutionary time scales and a focus on historical contingency, rather than predictable pattern, in his later work.