Social evolution and the individual-as-maximising-agent analogy

Abstract

Does natural selection tend to maximise something? Does it produce individuals who act as if they maximised something? These questions have long occupied evolutionary theorists, and have proven especially tricky in the case of social evolution, which is known for leading to apparently suboptimal states. This paper investigates recent results about maximising analogies – especially regarding whether individuals should be considered as if they maximised their inclusive fitness – and compares the fruitfulness of global and local approaches. I assess Okasha & Martens's recent local approach to the individual-as-maximising-agent analogy and its robustness with respect to interactive situations. I then defend the relative merits of a comparable global approach, arguing that it is conceptually on a par and heuristically advantageous.

Introduction

Does natural selection tend to maximise something? Does it produce individuals who act as if they maximised something? These two questions, or maximisation analogies, have long occupied evolutionary theorists. Early formal results suggested that natural selection acts so as to maximise mean fitness (Fisher, 1930). In contemporary evolutionary theory, the success of kin selection has caused many to consider that natural selection makes evolutionary individuals act as if they maximised their inclusive fitness. However widely – and perhaps falsely – believed, such claims have been mitigated or not formally established. According to their current interpretation, Fisher's results do not show that we should expect natural selection to cumulatively increase mean fitness; kin selection has led to a number evolutionary analyses but not to a justification of inclusive fitness maximisation. General criticisms about adaptationism, whether due to genetic constraints or to social contexts, have also fueled doubts as to whether natural selection should really be expected to maximise something at all.

Such frustrating results have led to a renewed exploration of the maximisation claims, through a number of frameworks. First, there are two distinct claims or analogies to explore, depending on whether nature or evolutionary individuals may be seen as maximisers. Second, there are two broad ways in which to explore them. Some start from general evolutionary results, which they hope to apply to concrete situations. Others aim to work their way up from maximisation results in specific contexts to more encompassing ones. Is one method preferable? How could we hope to generally determine the domain of validity of maximisation analogies - what maximises what under which conditions and in which evolutionary contexts?

This paper has two related aims. First, it intends to describe some recent works on maximisation analogies and assess their limitations. Second, it focuses on a recently developed approach in order to critically discuss its fruitfulness when compared to a rival approach, derived from Hamilton's rule, which has recently undergone criticism. Most of the paper focuses on the specific case of social evolution and on the question about whether evolutionary individuals maximise their inclusive fitness – which is probably the most widely believed maximisation claim in evolutionary theory. More precisely, I assess Okasha & Martens recent local approach to the individual-as-maximising-agent analogy, its robustness with respect to interactive situations. I then defend the relative merits of a comparable global approach, arguing that it is conceptually on a par and heuristically advantageous.

The paper unfolds as follow. Section 2 discusses two possible understandings of maximisation and two possible approaches – global or local – for exploring maximisation analogies. Section 3 surveys various global approaches used to investigate the maximising analogies in the context of social evolution and underlines their current limitations. Section 4 then tackles local approaches – so-called individual-as-maximising-agent analogies – focusing in particular on recent work by Okasha and Martens, and uses their very method to suggest that the existence of a general function that individuals would maximise is unlikely. Section 5 discusses the issue of individual control, which leads to one way of re-establishing the relevance and heuristic advantage of the global maximisation approach. Section 6 concludes on the fruitfulness of global and local approaches for the maximisation research program in evolutionary biology and mentions one avenue for future work.