THE LEGACY OF PUNCTUATED EQUILIBRIUM

The paleontological contribution for which Stephen Jay Gould is probably best remembered is punctuated equilibrium. Although punctuated equilibrium (not to mention Gould and Eldredge themselves) drew considerable criticism over the years, most would now agree that a punctuated pattern does prevail; a majority of fossil species appear abruptly on geologic time scales and exhibit only minor fluctuations of morphology over their lifetimes. A consensus as to what this pattern means, however, has not yet developed. Most problematic seem to be issues surrounding the association of morphologic change with speciation, and the notion and implications of species as individuals.

Punctuated equilibrium is typical of many of Gould’s ideas, in that it necessarily begins with detailed study of morphology, but has wide-ranging and important implications for evolutionary theory. The legacy of punctuated equilibrium is thus a large body of work on fossils with relevance to evolutionary mechanisms, and an ongoing tradition of detailed morphologic studies of geographic and temporal variation in fossil samples. Punctuated equilibrium brought paleontologists and biologists together in a dialogue that is critical to advancing evolutionary understanding. Finally, although punctuated equilibrium is specifically about species level patterns, part of its legacy is the widespread recognition of non-uniform rates of change across all of life’s history.