The Structure and Content of the Modern Synthesis

When taken together, the four books of Dobzhansky, Mayr, and Simpson, written as they were so closely together in time (and space—Columbia University and the American Museum of Natural History are within forty blocks of each other in New York City) reveal a relatively minor amount of disarray, a slight lack of cohesion in the early stages of the synthesis. That some of these discrepancies were later removed—most notably through a more universal acceptance of the dominant role of natural selection in effecting adaptive change (Gould 1980b)—is important, if only because it established more of a semblance of agreement and consensus. The acceptance that Mayr (1982, pp. 568-69) reports among nearly all participants at the Princeton conference held in 1947 seems real enough; by the late 1940s the final, polished version of the synthesis apparently had begun to emerge. But we must ask if there were any important additions to evolutionary theory after these four books appeared. Changes in emphasis—for example, on selection, but also in such issues as Mayr’s later (especially 1963) views on the role that species play in evolution—certainly did occur. And, of course, beyond the conceptual lies the straightforward discovery of new phenomena, such as the myriad wonders of the molecular biology of the gene, begun in earnest in the early 1950s and still being announced daily. What concerns me here is more the structure of evolutionary theory than its precise content. Have either new ideas or new data since the publication of these four books materially modified the way we think about evolution? The answer, for the most part, is no; the theory presented in the better recent college textbooks (e.g., Dobzhansky et al. 1977; Futuyma 1979) is substantially the same as the amalgam that arose from the four books analyzed here, with the rough edges sanded and recent discoveries—nearly all concerning the molecular structure of the gene—duly incorporated. But there were some particularly important innovations and shifts of emphasis within the purview of the synthesis.