Historical Significance of George Gaylord Simpson’s Tempo and Mode in Evolution (1944)

Simpson (1944) Tempo and mode in Evolution, figure 30

Cain, Joe. 1989. Moving Beyond Consistency: The Historical Significance of Simpson’s Tempo and Mode in Evolution. Unpublished MA thesis. University of Maryland College Park.


Simpson’s (1944) Tempo and Mode in Evolution (TM) is a complex book. TM’s content and significance have been poorly examined previously. My integrated analysis emphasizes two themes. First, Simpson elaborated a comprehensive evolutionary theory. Second, Simpson pursued different agendas with different audiences. TM defended a particular synthetic theory against alternatives. Also, TM supported a particular inter­school conceptual unification: Morgan’s chromosome theory of heredity, Wrightian population genetics, adaptation via natural selection, and Simpson’s temporal approach to evolution. TM was well received among paleontologists, who largely adopted Simpson’s conclusions as the foundation for their research; however, biologists mostly favored extrapolationist alternatives instead of Simpson’s agenda, citing TM only to validate particular explanatory tools.

I untangled three conflated uses of the “consistency” argument for TM: literal consistency, extrapolation, and a shared explanatory tool box. The latter most precisely describes (1) the relation between Simpson and other MS synthetic theorists, and (2) the relation between Simpson’s explanations for micro-, macro-, and mega-evolution. This topic provides only one (and not the most significant) point regarding TM. Simpson’s other agendas were separable from the construction of his comprehensive theory, as TM was far more than a “consistency” argument.

A research school-level of analysis provides a finer-grained study of synthetic theories. This recognizes Simpson’s intellectual achievements plus the dissent within individual fields. Also, it allows for a study of the competition between conflicting synthetic theories. Furthermore, the study of explanatory tool boxes provides an alternative method for studying evolutionary theorists.

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