STEPHEN JAY GOULD: HIS EVOLVING, HIERARCHICAL THOUGHTS ON STASIS

Stephen Jay Gould's scientific legacy is impressive, covering numerous important topics in paleontology and evolutionary biology; arguably one of his most important contributions is his work developing the theory of punctuated equilibrium along with Niles Eldredge. This theory was important for many reasons including that it signified paleontology was a discipline that could make fundamental contributions to evolutionary biology. Gould's work, along with Eldredge, on punctuated equilibrium focused on several topics including: its relevance to trends in the history of life; hierarchy theory; and the role of competition in evolution. One area that Gould devoted research to was the mechanisms that cause species to show morphological stasis over remarkably long periods of time, much longer than predicted by standard Darwinian models. Originally, Gould primarily emphasized the role that developmental constraints might play in mediating stasis. His views on the nature of species stasis and also the tempo of change at the time of divergence were incorrectly presented by some evolutionary biologists as a caricature of Goldschmidt's views on hopeful monsters, whereas they were actually much more complex. In fact, through time he came to rely not only on organismal development but also the population structure of species as an important mechanism that mediated stasis, and his views on this and other macroevolutionary topics were always explicitly hierarchical. This is especially evident in his book "The Structure of Evolutionary Theory." More recently the mechanism of stasis related to the population structure of species has also been incorrectly presented as derivative of another evolutionary biologist's ideas: this time Futuyma's. Here, in considering Stephen Jay Gould's scientific legacy I will focus on various mechanisms that contribute to evolutionary stasis, paying special attention to the roles of organismal development and the population structure of species.