 In recent years, a vigourous debate has opened up about whether the “modern synthesis” (MS) is still adequate to the needs of biology. The MS, or neo-Darwinian synthesis, is the intellectual edifice that arose in the 20th century from the integration of Darwin’s theory of evolution with Mendelian genetics, which had population genetics at its core, as we have seen. Proponents of the “extended evolutionary synthesis”, or EES, argue that the main principle of the MS—that adaptive evolution arises from natural selection acting on sporadic genetic mutation—is not wrong but is not the whole story either, and needs supplementation in the light of recent discoveries (Pigliucci and Muller eds. 2010; Laland et al. 2014, 2015). They point to phenomena such as niche construction, epigenetic inheritance, multi-level selection, phenotypic plasticity and developmental bias, which, they claim, do not fit easily with the MS’s emphasis on gene-based evolution. The EES’s proponents are typically somewhat suspicious of population genetics, and seek to downplay its explanatory significance. However, their views are controversial. Defenders of the traditional MS argue that the empirical phenomena in question are of relatively minor evolutionary importance and / or that they can be accommodated within the MS without any major paradigm shift (Wray et al. 2014; Walsh and Lynch 2018; Charlesworth, Barton and Charlesworth 2017). This debate looks set to continue.