Speciation—the origin of new species—has been one of the most active areas of research in evolutionary biology, both during, and since the Modern Synthesis. While the Modern Synthesis certainly shaped research on speciation in significant ways, providing a core framework, and set of categories and methods to work with, the history of work on speciation since the mid-twentieth century is a history of divergence and diversification. This piece traces this divergence, through both theoretical advances, and empirical insights into how different (...) lineages, with different genetics and ecological conditions, are shaped by very different modes of diversification. (shrink)

Ecology in principle is tied to evolution, since communities and ecosystems result from evolution and ecological conditions determine fitness values. Yet the two disciplines of evolution and ecology were not unified in the twentieth-century. The architects of the Modern Synthesis, and especially Julian Huxley, constantly pushed for such integration, but the major ideas of the Synthesis—namely, the privileged role of selection and the key role of gene frequencies in evolution—did not directly or immediately translate into ecological science. In this paper (...) I consider five stages through which the Synthesis was integrated into ecology and distinguish between various ways in which a possible integration was gained. I start with Elton’s animal ecology, then consider successively Ford’s ecological genetics in the 1940s, the major textbook Principles of animal ecology edited by Allee et al., and the debates over the role of competition in population regulation in the 1950s, ending with Hutchinson’s niche concept and McArthur and Wilson’s Principles of Island Biogeography viewed as a formal transposition of Modern Synthesis explanatory schemes. I will emphasize the key role of founders of the Synthesis at each stage of this very nonlinear history. (shrink)

This paper surveys questions about the nature of the Modern Synthesis as a historical event : was it rather theoretical than institutional? When and where did it actually happen? Who was involved? It argues that all answers to these questions are interrelated, and that systematic sets of answers define specific perspectives on the Modern Synthesis that are all complementary.

I propose we abandon the unit concept of "the evolutionary synthesis". There was much more to evolutionary studies in the 1920s and 1930s than is suggested in our commonplace narratives of this object in history. Instead, four organising threads capture much of evolutionary studies at this time. First, the nature of species and the process of speciation were dominating, unifying subjects. Second, research into these subjects developed along four main lines, or problem complexes: variation, divergence, isolation, and selection. Some calls (...) for 'synthesis' focused on these problem complexes (sometimes on one of these; other times, all). In these calls, comprehensive and pluralist compendia of plausibly relevant elements were preferred over reaching consensus about the value of particular formulae. Third, increasing confidence in the study of common problems coincided with methodological and epistemic changes associated with experimental taxonomy. Finally, the surge of interest in species problems and speciation in the 1930s is intimately tied to larger trends, especially a shifting balance in the life sciences towards process-based biologies and away from object-based naturalist disciplines. Advocates of synthesis in evolution supported, and were adapting to, these larger trends. (shrink)