The Darwinian Core of Evolutionary Theory and the Extended Evolutionary Synthesis: Similarities and Differences

In this chapter, we evaluate debates surrounding calls for an Extended Evolutionary Synthesis in light of the Darwinian core of evolutionary theory, which was somewhat broader than the Modern Synthesis. We suggest that Darwin’s nuanced operationalization of natural selection rested upon two innovations: the atomization of individuals into trait-variants, and a reconceptualization of heredity in terms of transmission of trait-variants. Darwin also implicitly differentiated between the causes and consequences of selection, noting that while selection acts on individuals, it is actually trait-variants that are consequently differentially transmitted, and the species that is eventually modified. This is important because the individual, with inherencies and agency, is largely relevant only when examining the causes of selection, with trait-variants being the more appropriate unit for studying its consequences. Consequently, we emphasize the importance of restricting the use of ‘fitness’ to one-step change in trait-variant frequency, instead of also using it for lifetime reproductive success of individuals, or even trait-variants. Fitness, thus defined, is always inclusive, circumventing much unnecessary debate. We also present a schematization of explananda in evolutionary biology and suggest a framework for the comparative evaluation of factors affecting evolutionary change. We further suggest that the controversial ‘gene’s eye view of evolution’ is best seen as not one, but two distinct views, one Fisherian and the other Dawkinsian, and that conflating them has led to considerable unnecessary debate. In conclusion, we suggest that it is helpful to view received evolutionary thought as an evolving set of explanations, intertwined with one another to varying degrees, rather than a distinct, static Modern Synthesis. This leads to our viewing various processes and factors affecting the origin, dynamics and patterns of prevalence of variants at various levels of biological organization, as representing differing but complementary parts of a complex, nuanced, multifarious and evolving standard evolutionary theory.