For the past five decades, evolutionary biology has been the stage for a persistent and ongoing scientific controversy. This controversy is about the question whether the dominant version of evolutionary theory – the modern synthesis – needs to be reformed and expanded. It has been characterized by the opposition between two broad camps: the reformists and the conventionalists. The reformists have argued that the modern synthesis has outlived its usefulness, in some important sense, and needs major reform. The conventionalists have opposed these claims, generally arguing that all empirically adequate reformist proposals can be incorporated into the modern synthesis without fundamentally changing that synthesis or our view of evolutionary theory. The result has been a continuous and complex scientific controversy about the structure and content of evolutionary theory – here called the extension controversy.

In this project, I focus on reformist thought, particularly as it was developed in palaeontology, evolutionary developmental biology (EvoDevo), and the ‘Extended Evolutionary Synthesis’ (EES). My aim is to lay an important part of the foundation of an understanding-based account of the extension controversy by (i) determining the leading epistemic considerations that have motivated reformist critiques of the modern synthesis and (ii) to determine the extent to which these critiques constitute, and came to constitute, a coherent reformist position. Thus, this project consists in a comparative analysis of various phases of reformist critique of the modern synthesis, starting in the 1970s with palaeontology, followed by EvoDevo, and leading up to the EES. This comparative analysis of reformist thought relies on recent advances in integrated history and philosophy of science (&HPS) and the epistemology of scientific understanding. As such, this project should be interest to historians and philosophers of science, as well as historically minded evolutionary biologists, and the current generation of reformists.