01-Dunbar-Chap01 12/22/06 3:40 PM Page 3 CHAPTER 1 Evolutionary psychology in the round Robin Dunbar and Louise Barrett 1.1. Introduction questions that biologists can ask, the other two being questions about function (a teleonomic Although the closing decades of the nineteenth question that is, ultimately, about the genetic con- century witnessed a great deal of interchange sequences of behaviour) and phylogeny (the evo- between psychology and evolutionary biology, lutionary history of how a behaviour came to the hasty departure of James Baldwin from the have its current form). Tinbergen (1963) pointed American psychological scene in 1908 (thanks to out that all four provide appropriate answers to the scandal of being caught in a brothel) trig- the generic question ‘Why does an animal do X?’; gered, for reasons that are more political than sci- all must in the end be answered for a full under- entific, the virtual severance of contact between standing, but each can be asked and answered the two disciplines (Plotkin, 2004). Psychology independently. That is to say, our answer to one became more heavily influenced by its alternate does not necessarily commit us to any particular roots in physiology and the neurosciences, on the answer for any of the others. one hand, and the social sciences, on the other. We want to make two general points in this Evolution played no significant role in psychology chapter. First, the evolutionary approach neces- for the better part of a century. Indeed, the 1950s sarily enjoins us to take a broad disciplinary per- in particular witnessed a somewhat tetchy quarrel spective to our subject matter (which, following between the comparative psychologists (with Heyes (2000), we might refer to as ‘evolutionary their feet firmly planted in behaviourism and an psychology in the round’). Second, an evolution- experimental paradigm) and the ethologists (with ary view does not—and should not—commit us their roots in evolutionary biology, and a focus on to any particular assumptions about the genetic the observational study of an animal’s behaviour determination of behaviour. Indeed, learning, in its natural environment). and by extension cultural transmission, play an In part, this drift away from biology reflected an especially important role in the behaviour of increasing focus within academic psychology on humans, and we will never be able to understand questions of mechanism (with a broad focus on human behaviour without understanding cul- stimulus–response processes, motivation, cogni- ture and the way it influences what humans do. tion and, later, neuropsychology) and develop- These issues are explored in more detail else- ment. For the ethologists, these constituted just where in this volume, but our main concern here two of what eventually came to be known as is to provide a framework within which the ‘Tinbergen’s Four Why’s’—the four kinds of chapters that follow can be understood. 01-Dunbar-Chap01 12/22/06 3:40 PM Page 4 4·CHAPTER 1 Evolutionary psychology in the round 1.2. Asking the right questions versus ontogenetic (i.e. developmental) questions. Questions about genetic determinism belong to The important consideration in the present con- the realm of ontogeny (how the individual text is that evolutionary (or Darwinian) theory acquires its capacities during the course of devel- provides a framework within which a diverse opment), but the core to an evolutionary approach range of intellectual questions can be integrated. lies in function (questions about the evolution- The significance of this is well illustrated by the ary goal-directedness of these capacities and the role it has played within biology. A century ago, behaviour they make possible). biology consisted of half a dozen or more quite Of course, as an essentially biological question, separate disciplines (anatomy, zoology, botany, the primary focus of functional questions lies in genetics, physiology, microbiology, biochem- how an organism’s behaviour maximizes its istry, etc.) that rarely interacted. The gradual genetic fitness. But the fact that an individual acts acceptance of the theory of evolution as a central so as to maximize its fitness does not mean that organizing principle has made it possible for its behaviour is genetically determined, merely these diverse interest groups to talk to each other that it has a set of genetically inherited motiva- in a common language in a way that had rarely tions (or goal states) that it seeks to satisfy. How been possible in the past. it achieves those goal states will, at least in neu- Our claim here is that an evolutionary approach rologically advanced species, depend on the can and should do the same for psychology. individual’s assessment of the costs and benefits Evolutionary psychology, we argue, is not a new of acting in one way rather than another, given its and separate sub-discipline within psychology, experience of the world. In evolutionary biology, but rather a framework theory that allows psy- every decision is a contingent one that depends chology’s many diverse sub-disciplines to be on the details of the context. That context will integrated into a unitary whole. It is not our obviously include many features of the physical intention to demonstrate this claim here by environment, but in highly social species like showing how different psychological approaches humans it will also include the social environ- could relate more effectively to each other. ment. We return to this point again below. The Rather, our aim is simply to make it clear that a issue here, however, is that the genes that are developmental stance, for example, is not differ- passed on from one generation to another need ent from, or in intellectual opposition to, an be not the genes for a particular behaviour, but evolutionary approach. Rather, an evolutionary may, rather, be the genes for a brain that is large perspective adds to a developmental approach enough, and complex enough, to make the deci- by offering new ways of seeing development, sions about how best to act in order to satisfy prompting novel questions for empirical study, its motivations (thereby maximizing fitness). and, more broadly, allowing developmental psy- Questions about the roles of genes and the envi- chologists to integrate their findings with those ronment in the production of those brains, or of neuropsychologists, cognitive psychologists any other aspect of the system, are of course and others. Life history theory, for example, is interesting, but they remain quite separate, and major feature of contemporary evolutionary are unaffected by the extent to which an individ- ecology, with enormous relevance both to repro- ual can be shown to be maximizing its fitness. ductive decision-making and to development. The issue of ontogeny is, of course, an impor- Yet, its implications have only recently begun to tant one that has been the focus of yet another be explored. Several of the chapters in Section V long-running debate within psychology in par- draw on it in their explorations of different ticular (the so-called nature/nurture debate). aspects of human reproductive behaviour. Biologists have largely accepted, since the 1960s, In this context, it is particularly important to that this distinction is arbitrary and, worse still understand that an evolutionary approach does perhaps, misguided. We cannot separate genes not commit us ipso facto to genetic determinism. from the environment in the simple-minded To assume that it does is to commit a classic cat- way implied by this dichotomy. Both nature and egory mistake by failing to distinguish two of nurture are deeply implicated in the processes of Tinbergen’s Four Why’s—functional questions development, even though it may be possible to 01-Dunbar-Chap01 12/22/06 3:40 PM Page 5 Asking the right questions · 5 discuss the magnitude of the relative contribu- rump on the periphery where they continued to tion of genetic versus environmental effects to focus on somewhat arcane topics like intelligence the differences between individuals. Nonetheless, and personality theory. The rise of evolutionary no aspect of an organism’s biology or psychology ideas in the study of animal behaviour during can be said to be wholly (or even mainly) due to the 1970s (originally in the form of a sub- its genes or the environment in which it grows up. discipline that named itself sociobiology, but The distinction, nonetheless, is important in which later adopted the alternative name behav- one key respect. If we recognize that questions ioural ecology) seems to have been viewed by the about the mechanisms of inheritance are separate naturists as offering something of a bulwark from questions about the evolutionary function against the nurturists, in part at least because it of behaviour, then the way is opened up for the seemed to imply some form of genetic basis for evolutionary study of culture as an important cognition and behaviour. phenomenon in its own right. Self-evidently, cul- This may, in turn, provide us with a way ture depends on learning—specifically the social of articulating the equally fractionated sub- transmission of beliefs or rules of behaviour— disciplines of evolutionary psychology. Since the but learning is simply another mechanism of mid-1990s, evolutionary psychologists have inheritance in the grand evolutionary scheme. been embroiled in what might seem like an Biologists’ perennial focus on genes (and, more internecine war between those whose intellec- recently, DNA) as the mechanism of inheritance tual tradition lay within behavioural ecology is, perhaps, to be expected given their interest in (who sometimes refer to themselves as evolu- the more hard-wired aspects of biology, such tionary anthropologists) and those whose intel- as anatomy. But it is crucial to remember that lectual tradition lay within psychology (who neither Darwin nor Mendel (widely considered originally referred to themselves as Darwinian to be the founding father of genetics) actually psychologists, but later co-opted the term ‘evo- knew anything about genes or DNA.