The Curious Incident of the Wasp in the Fig Fruit: Sex Allocation and the Extended Evolutionary Synthesis

How would we tell if we needed a new evolutionary synthesis? The rationale for the so-called Extended Evolutionary Synthesis (EES) is predicated on there being limitations, failings, or something missing from the current body of theory that evolutionary biologists use when seeking evolutionary explanations for the patterns of biodiversity we see around us. A number of topics have allegedly been neglected or obscured by evolutionary biologists, including the role of development in evolution (“evo-devo”), phenotypic plasticity, niche construction, behaviour, epigenetics, and trans-generational effects. These disparate topics more or less coalesce around two organising principles of EES thinking, that of organismal agency and non-genetic inheritance. In this chapter, I use the field of sex allocation to test the validity of the arguments that these topics have indeed been neglected. Sex allocation is a useful exemplar of evolutionary biology. Thanks to Fisher and Hamilton, it has a historically rich and well-understood theory base. Moreover, across more than five decades, there have been hundreds of empirical tests of components of that theory, across a huge diversity of organisms, such that sex allocation is one of the most successful and well-validated fields within evolutionary biology. If claims of the EES have credence, then the study of sex allocation should clearly highlight what we have missed or ignored. However, I show that all of the components put forward by proponents of the EES as needing to be added into evolutionary biology—with perhaps the exception of cultural evolution, as least outside of humans—have long been studied, implicitly and explicitly by those studying sex allocation. In many cases, the relevant concepts are there at the inception of the modern study of sex allocation, following Hamilton’s ground-breaking paper in 1967. Having dispensed with the need for the EES, I finish by trying to understand why such a synthesis was ever called for in the first place.