Understanding behavioural innovation, novelty and evolvability

Abstract

The depth of the influence of Ernst Mayr's famous proximate-ultimate distinction in biology is reflected in the widespread assumption that developmental processes are irrelevant to our understanding of evolution and vice versa. The field of evolutionary developmental biology (Evo-devo) challenges this assumption by taking seriously the potential for developmental processes to have long-lasting evolutionary effects. To date, the impact of the Evo-devo "revolution" has been almost entirely restricted to the morphological domain - discussions of the role of contingency and development in the evolution of morphological traits being commonplace. In contrast, very little attention has been paid to contingency and development in the evolution of behavioural traits. This observation leads one to ask two obvious questions: (1) are there any in-principle reasons why this is the case? And, (2) what would happen if such concepts were used when thinking about behavioural evolution? This thesis responds to these questions. The thesis is broken into three parts. In the first, I motivate the application of the conceptual toolkit from Evo-devo to the behavioural domain. To do so, I argue that there is evidence that development plays an important causal role in the evolution of behavioural traits that is as strong as, if not stronger, than the analogous evidence used to motivate the Evo-devo approach in the morphological domain. On these grounds, we should be just as willing to engage in the Evo-devo research program when considering the evolution of behavioural traits as we are when considering the evolution of morphological traits. Having motivated thinking about the evolution of behaviour from within the Evo-devo paradigm, I turn to the application of the Evo{u00AD}devo conceptual toolkit in the behavioural domain in the latter two parts of the thesis. In the second part of the thesis, I present revised accounts of the central concepts of "evolutionary novelty," "innovation" and "evolvability" that are broad enough to allow the discussion of behavioural evolution from the Evo-devo perspective. In the third and final part of the thesis, I use these revised concepts to consider the impact that learning (when a capacity of the individuals making up a population) can have on evolvability. I demonstrate that the capacity for even simple, and quite rigid, forms of learning in the individuals that make up a population can influence the evolvability of that population by protecting the standing phenotypic variation from sudden environmental change. I argue also that more complex and flexible learning systems can confer even greater evolutionary benefits on populations by influencing the rate and direction of evolutionary change.