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This chapter examines the notorious issue of group selection in behavioural ecology, one of the mainstays of the traditional levels of selection debate. The history of the group selection controversy is briefly traced. The relationship between group selection, kin selection, and evolutionary game theory is discussed. An important debate between Sober and Wilson and Maynard Smith concerning the correct way to conceptualize group selection is explored. Lastly, some arguments of L. Nunney concerning the distinction between weak and strong altruism, and how individual and group selection should be defined, are examined.

In the 1970s game theory made several appearances in evolutionary biology that led to enduring theoretical traditions within the field – most notably, the concept of an “evolutionarily stable strategy” to explain the evolution of restrained aggression in animal fights, and the use of repeated Prisoner’s Dilemma games to explore phenomena of “reciprocal altruism.” This chapter argues that these appropriations of game theory were facilitated by shifts in ideas and working practices inside biology, and by changes in the received impression of game theory as a result of the arms control debates. Earlier explanations of “social” adaptations in terms of collective benefit were displaced by explanations invoking benefits to individuals or genes. This intellectual change was paralleled by methodological shifts from descriptive field biology toward mathematical modeling and computer simulations of evolutionary processes. Game theory, recast by its sojourn in conflict resolution as a notational system for exploring the logic of conflict and cooperation and the relationship between individuals and groups, proved irresistible to biologists seeking explanations of social phenomena in terms of its benefit to individuals. Yet ironically, they were attracted to game theory for what they saw as its denial of “rationality” or “choice” to the “game-players” in question.

Rationality and evolution are apparently quite different, applying, respectively, to the acts of complex, well-informed individuals and to populations of what may be mindlessly simple entities. So it is remarkable that evolutionary game theory shows the theory of rational agents and that of populations of replicating strategies to be isomorphic. Danielson illustrates its main concepts—evolutionarily stable strategies and replicator dynamics—with simple models that apply to biological and social interactions; and he distinguishes biological, economic, and generalist ways of interpreting the theory. Against the background of isomorphism, he considers three ways in which evolution and rationality differ and how two-level models may combine them. He concludes with a survey of the normative significance of the unification of rationality and evolutionary game theory and some speculation about the evolution of human rationality.

Selection is often generated by interaction with other organisms: neighbours, partners, or antagonists. The force and direction of selection in these social contexts is very generally influenced by the density and composition of the population. It may result in some degree of cooperation or helpfulness, rather than unrestricted competition among individuals. The first section here is called Selection within a single uniform population: density-dependent selection and details density regulation; density-dependent fitness; the principle of frugality; resource competition in continuous culture; r-K selection; r-K selection experiments; and selection in seasonal environments. The second section is called Selection within a single diverse population: frequency-dependent selection and describes GxG; frequency-dependent fitness; and also frequency-dependence in complex environments. The third section is about social behaviour and describes the phenotypic theory of aggression and exploitation; cross-feeding; selfish cooperation; the prisoners' dilemmas; intransitive social interactions; and time-lagged social interactions. The final section is called Kin selection and group selection and describes kin selection; kin proximity and kin choice; spite; group selection in structured populations; productivity and diversity; artificial group selection; and cultural evolution.

The chapter shows that a simple heuristic, which directs cooperation toward economic equals and defects on other individuals, facilitates cooperation in social environments where individuals engage in multiple, nonrepeated prisoner's dilemma games with partners whom they know little about. The heuristic produces successful cooperation due to its ability to infer whether or not its partner in a social encounter employs the same heuristic—not whether that partner is cooperative per se. As noted in previous research and elaborated upon here, this property prevents the heuristic from suffering exploitation and it also impedes easily exploited cooperative strategies from proliferating in conditions of ubiquitous cooperation. These aspects of the strategy, furthermore, yield insight into the environments in which the heuristic fosters high levels of cooperation. The heuristic best succeeds at producing cooperation in social environments where agents involve themselves in a moderate number of low information, one-shot prisoner's dilemma games per generation. As the number of such encounters increases per generation, the strategy more frequently defects on its social partners. Nonetheless, the heuristic cultivates cooperation in social environments where interactions are not repeated, opportunities for punishment do not exist, and agents have no direct information about their partner's past cooperativeness.

This final chapter presents some general guidelines for thinking about the structure of our reasoning about norms. It begins with a dismissal of a purely evolutionary perspective on the contents of cultural systems, in favor of a more rational, reconstructive approach. It goes on to trace out the relationship between conventional morality and the more idealized constructions that philosophers typically have in mind when they speak about “morality.” The latter is identified as a type of expressive vocabulary that facilitates the development of critical reflection upon the former. Speculations on the origins and nature of the “moral point of view” are also advanced.

Drawing upon work in experimental philosophy and evolutionary game theory, the chapter argues that one of the roles the concept of knowledge plays in our social cognitive ecology is that of enabling us to make adaptively important distinctions between different kinds of blameworthy and blameless behaviors. In particular, the chapter defends the view that knowledge enables us to distinguish which agents are most worthy of blame for inflicting harms, violating social norms, or cheating in situations of social exchange.

Chapter 5 explores the reasons behind, and potential solutions for, asymmetric tokenism. The chapter shows that minority group members face a coordination problem when their group size grows to a critical mass, or the point at which they ought to be able to work together effectively. Minority group members remain “stuck” in the inefficient equilibrium of working with members of the majority. The chapter presents a simple evolutionary game theoretic model whereby coordination with “invaders” of an extant population becomes possible. The implications of that model are then tested using leadership PAC contributions from U.S. Senators, both to incumbents and challengers. A double-hurdle regression model provide evidence that although male Senate incumbents devalue both female incumbents and challengers, female Senate incumbents differentiate between incumbents and challengers in their valuation decisions. Specifically, women value challenger women more highly than incumbent women, indicating evidence of attempting to coordinate with potential newcomers.

This chapter looks at evolutionary models capable of representing the emergence of conventions between actors in different social groups. From a starting point of uncoordinated behavior, groups move toward states where everyone follows unified patterns in a way that tends to lead to successful outcomes. This cultural evolution is driven by social learning. Once groups have arrived at these coordinated behaviors they tend to remain there, so that the patterns of behavior persist over time. As the chapter shows, the addition of social categories radically changes the cultural evolutionary process. In particular, groups with categories reach the inequitable, but efficient, outcomes described in the last chapter.

Resources are often scarce, and scarcity often leads to conflict. The form of conflict ranges from subtle supplants in which one animal departs at the other's approach to escalated fights in which participants are seriously wounded. Interestingly, conflicts in a wide range of species are often resolved without dangerous escalation. In 1973, the eminent geneticist John Maynard Smith and an eccentric retired engineer named George Price explained why sometimes selection favored restraint, and why sometimes it didn't. This model, called the Hawk-Dove game, illustrates the power of simple models and changed the way biologists viewed animal contests. The Hawk-Dove game provides a simple introduction to a key feature of social behavior—individual fitness typically depends on the behavior of others. This chapter examines the Hawk-Dove game and some of its many descendants. It first introduces the basic ideas of evolutionary game theory and applies them to the understanding of the evolution of animal contests. It then discusses the results of the Hawk-Dove game for retaliation, evolutionary stable strategies, continuous stable strategies, ownership, resource holding power, and sequential play.

In the animal world, collective action to shelter, protect, and nourish requires the cooperation of group members. Among humans, many situations require the simultaneous cooperation of more than two individuals. Most of the relevant literature has focused on an extreme case, the N-person Prisoner’s Dilemma. Here we introduce a model in which a threshold less than the total group is required to produce benefits, with increasing participation leading to increasing productivity. It constitutes a generalization of the two-person Stag Hunt game to an N-person game. Finite and infinite population models are studied—in infinite populations a rich dynamics admits multiple equilibria. Scenarios of defector dominance, pure coordination, or coexistence may arise simultaneously. However, populations are finite and when their size is of the same order of magnitude as the group size, the evolutionary dynamics is profoundly affected: it may ultimately invert the direction of natural selection, compared with the infinite population limit.

This chapter aims to illustrate evolutionary explanations for the emergence of framing effects, discussed in detail in Cristina Bicchieri’s The Grammar of Society. It shows how framing effects might evolve which coalesce two economically distinct interactions into a single one, leading to apparently irrational behavior in each individual interaction. Here it considers the now well-known example of the ultimatum game, and shows how this ‘irrational’ behavior might result from a single norm, which governs behavior in multiple games. The chapter also shows how framing effects might result in radically different play in strategically identical situations. It considers the Hawk–Dove game (the game of chicken) and also the Nash bargaining game. Here arbitrary tags or signals might result in one party doing better than another.

Collaboration is increasingly popular across academia. Collaborative work raises certain ethical questions, however. How will the fruits of collaboration be divided? How will academics divide collaborative labor? This chapter considers the following question in particular. Are there ways in which these divisions systematically disadvantage certain groups? The chapter uses evolutionary game theoretic models to address this question. First, it discusses results from O'Connor and Bruner (2015) showing that underrepresented groups in academia can be disadvantaged in collaboration and bargaining by dint of their small numbers. Second, it presents novel results exploring how the hierarchical structure of academia can lead to bargaining disadvantage. The chapter investigates models where one actor has a higher baseline of academic success, less to lose if collaboration goes south, or greater rewards for non-collaborative work. The chapter shows that in these situations, the less powerful partner can be disadvantaged in bargaining over collaboration.

This chapter does two things. The first is to use the evolutionary framework developed to explain a particular feature of the gendered division of labor—that some aspects of it seem conventional, and other less so. In developing this argument, the chapter employs a novel measure intended to capture the way conventionality can vary in degrees. The second is to explain why, somewhere between our most recent common ancestor and now, gender emerged in human groups. Some social scientists have argued not just that gender facilitates division of labor, but that gender itself exists in order to divide labor. The chapter presents a how-possibly model for the emergence of gender in a society without it.

The chapter starts with an introduction of the primary paradigm used in this half of the book—the bargaining game. It uses this model to show why in groups with social categories fairness in bargaining is not the expected outcome of cultural evolution. Instead, social categories act as a symmetry breaker that stabilizes inequitable bargaining conventions. The chapter then turns to the role power plays in the evolution of bargaining. Powerful groups often gain an advantage with respect to the emergence of conventions of resource division. This can lead to compounding processes that profoundly disadvantage some social groups. These models make especially clear how irrelevant markers like race and gender can come to be more important in determining resource division than relevant factors, such as individual status.

Natural selection is the scientific explanation for the evolution of adaptations. Wonders of the living world, such as the anatomy and physiology that grants the cheetah its unchallenged running speed; the seductive colors and scents of a flower that are irresistible to its pollinators; and the accuracy and sophistication of sense organs such as the human eye are the ultimate results of this one creative force in evolution. This chapter investigates simple models of natural selection to explore its power in causing evolutionary change. Mathematical techniques including invasion fitness analysis and adaptive landscapes are powerful tools for analyzing such models and for identifying evolutionarily stable and unstable equilibria. The chapter further investigates frequency-dependent selection and evolutionary game theory. An important goal here is to show that selection can take many different forms and yield very different evolutionary outcomes.