Evolutionary psychology Evolving theories of behaviour VER a relatively short period of time evolutionary psychology O has become a prominent way of understanding the human mind and behaviour. Its origins lie in a number of JOHN ARCHER describes a rich research agenda for theoretical analyses of animal behaviour in the 1960s and early 1970s which evolutionary psychology in testing novel hypotheses. transformed the way this subject was studied and understood. Just as the often provide new ways of viewing existing discipline at the time. Conventional social evolutionary approach led ethologists phenomena, and therefore aid overall psychology assumes that human behaviour away from concentrating on the immediate understanding of psychological can be explained in terms of culture-specific causal mechanisms controlling animal phenomena, but the speculations social learning, with relatively little behaviour, so evolutionary psychology themselves may be difficult to test contribution from evolved dispositions seeks to lead conventional psychologists empirically. to act in particular ways. In contrast, away from explanations that concentrate These considerations apply to one evolutionary psychology involves thinking only on immediate mechanisms and mental strand of evolutionary thinking, that about human beings in ways that generate events. Instead it offers a single unifying concerned with the origins of present-day novel testable hypotheses that would have starting point for understanding why we behaviour, and its original adaptive been beyond the scope of conventional think and behave as we do today: natural significance. Consideration of adaptive social science thinking (provocatively selection has made us this way. significance is (as the pioneering ethologist referred to as the SSSM or standard social This simple statement hides a number Niko Tinbergen (1963) pointed out) science model by Tooby & Cosmides, 1992). of complexities that need to be understood a different type of explanation from that There would have been no reason for before the powerful insight can be involving immediate causal mechanisms, a conventional social psychologist working translated into an effective research agenda. which is the concern of most psychologists, within the SSSM to have thought that In this article I deal with two of these whether traditional or evolutionary. stepchildren should be at any greater risk complexities that often lead to Evolutionary psychologists tend to than natural children for child abuse or misunderstandings both within and outside combine evolutionary biology’s emphasis homicide; that the relatives of new-borns the evolutionary perspective. They are, on ultimate or functional explanations, with should comment disproportionately on the first, how specific evolutionary hypotheses psychology’s emphasis on the immediate infant’s resemblance to the father rather are derived from broader evolutionary causes of human behaviour. The way the than the mother; that a man’s degree of principles, and second, the limitations of two are linked is expressed in phrases such bodily symmetry would have any impact the assumption that human behaviour is as ‘the past explains the present’ (Tooby & on his sexual attractiveness; that human adaptive in an evolutionary sense. Cosmides, 1990, p.375), or ‘we are sexual psychology is influenced by sperm walking archives of ancestral wisdom’ competition; and that the ratio of the length Origins and mechanisms (Cronin, 1991, p.3). The connection is also of the second and fourth digit is related to One common dismissive view of seen in the principle referred to as ‘reverse musical ability. But these are among the evolutionary psychology is that it engineering’ of a particular trait or often counter-intuitive hypotheses that have represents a series of just-so stories based disposition (Pinker, 1997) – using present- been generated by an evolutionary on imaginary scenarios of Stone Age life. day construction to reveal the adaptive approach to human social life. This is a misconception, but it is one that significance. There are, therefore, two major is based on the self-evident truth that we By viewing present-day mechanisms as contributions of the evolutionary approach. cannot know the precise circumstances reflections of past adaptations, novel ways It provides informed speculations about the under which the human species evolved, or of looking at human behaviour are evolutionary origins of human behaviour, the social organisation of early hominids. generated, along with testable hypotheses and generates novel testable hypotheses Instead informed speculations are based on about present-day dispositions and the about current psychological mechanisms. various types of indirect evidence, notably mechanisms controlling them. Just as the Although the first is useful for an overall broad evolutionary principles, cross-species scope of social scientific inquiry is understanding of psychological comparisons, cross-cultural surveys, and constrained by its sociopolitical context, phenomena, it is the second that is present-day human behaviour. These so too is it constrained by the ideas that are important for establishing evolutionary informed speculations about origins can generated by the shared assumptions in the psychology as a research-based discipline. 414 The Psychologist Vol 14 No 8 August 2001 Peer commentary A hierarchy of hypotheses Buss did not explain his fourth- or ones, or where it was older females who Critics of the evolutionary psychology lowest-level hypotheses in any detail, committed most violent acts. We would programme often confuse what is being but from the example in his diagram not expect men and women to be equally tested in empirical studies. Particular data they would appear to apply to even more discriminating or indiscriminate about their sets are viewed as supporting or refuting specific circumstances, and to involve choice of a sexual partner. All of these the ‘evolutionary approach’. They do not. further additional assumptions to those of could in principle occur if human They support specific hypotheses drawn the third level. An example provided by behaviour had been shaped only by the from evolutionary or non-evolutionary Buss was that women have evolved dictates of cultural and historical forces. views of human behaviour. preferences for men who are high in status. But such behaviour is rarely – if ever – This important distinction can be This is not a hypothesis that is directly observed even at the individual level. clarified in relation to the notion of derived from Trivers’s parental investment We note the saintly and other-worldly a hierarchy of levels of analysis involved theory, as is the impact of paternity character of people of a religious calling in evolutionary hypothesis testing (Buss, uncertainty on male sexual jealousy. who turn their backs on both their families 1990). At the top is the principle of natural Instead it is derived from the principle of origin and their future marriage selection, which informs the whole of that where males are likely to contribute prospects. The idea of gangs of elderly modern evolutionary thinking. This is not resources and time to child rearing, females female delinquents only exists in the bizarre being tested in specific studies, since it is should choose those males that show signs minds of Monty Python scriptwriters. The well-established as a mechanism for the of being able to do so. Buss has translated reality is that we can derive a fairly detailed generation of adaptive changes over time, this general principle into a specific picture about what to expect of the social and can only be assessed by considering hypothesis applying to the human case, life of humans from the knowledge that we a wide range of biological and geological which is that women should be attracted are mammals that have evolved through the evidence that has accumulated over the last to men with money and status. That many process of natural selection (Brown, 1991). two centuries. women are so attracted is not disputed, but Most of the research agenda of The next level down in the hierarchy whether this is a consequence of evolved evolutionary psychology involves levels of consists of broad principles governing the adaptations, or a pragmatic decision in theorising and hypothesis generation that evolution of social behaviour, such as kin societies where men control access to are removed in some way from these selection (Hamilton, 1964), reciprocal resources, is a matter of dispute (e.g. Buss, general principles. They involve additional altruism (Trivers, 1971), and the parental 1989; Eagly & Wood, 1999; Hrdy, 1997). assumptions, and can be regarded as third- investment theory of sexual selection The important point about this debate is or fourth-level evolutionary hypotheses in (Trivers, 1972). So it is proposed that that if the consensus of the evidence does Buss’s scheme. I have already referred to behaviour can be governed by a need to support the alternative non-evolutionary two examples, male sexual jealousy and help relatives and those who have given explanation, this will have falsified one women’s preference for high-status men, help, and mates are chosen on the basis particular lower-level evolutionarily- which involve applying general principles of the effort they will put into bringing up derived hypothesis, rather than the higher- derived from sexual selection theory to offspring. Again, these broad principles are level principle it