of a successful trader’ (Herbert 2015: 116–18, cited in Fine 2017: 151).
It is research into sex differences of this second kind which feminist writers were initially most concerned to contest. That is, they have been concerned to contest that psychological and behavioural differences are anchored primarily in biological ones. In the debates surrounding such research into psychological and behavioural sex differences there are two steps which need to be evaluated. First is the claim that there are empirically significant differences between the psychological characteristics and behavioural dispositions of those people classified as male or female, men or women. Second is the claim that these psychological and behavioural differences are to be explained by biological features, by hormones, genetic variations anchored in chromosomes, and/or differences in male and female brains – biological traits whose presence is frequently explained by evolutionary selection. As Deborah Cameron noted in 2007, from the 1990s a ‘steady trickle of books’ about the sex differences of men and women ‘began to develop into a raging torrent’; from scientific papers which appear to suggest cognitive or behavioural differences, to popular science books and self-help books designed to aid communication across the presumed gap between men (who are from Mars), and women (who are from Venus), to coin an ubiquitous current usage’ (2007: 2).
It is not possible here to give a comprehensive review of the research into psychological and behavioural sex differences, and there are some really excellent texts which provide a critical review of this work, from biologists, psychologists and historians of science (see, for example, Bleier 1984; Fausto-Sterling 1992, 2000; Fine 2012, 2017; Cameron 2007; Jordan-Young 2010). It is, however, worth looking at examples of currently active research to give a sense of the kinds of difficulties surrounding it. If biological explanations are to be offered for psychological and behavioural differences between men and women, then these differences must themselves be established. Clearly, if we look around us, wherever we are, there are a large number of psychological and behavioural differences between those classified as men and those classified as women. But if these are to be biologically based then they must not be differences that vary historically or cross-culturally. Moreover, once we add that restriction, then the characteristics for which we might seek biological explanations become much fewer and highly contested.
The biological explanations offered for the supposed differences currently utilize two, often interwoven, strands of theory. One is evolutionary psychology. The second is research into differences between male and female brains.
Evolutionary psychology
Evolutionary psychology is a development from sociobiology, which assumes that behavioural differences between men and women of multiple kinds are adaptive for survival and have been selected in a process of evolution. The work of sociobiologists suggested that our genes programme our behaviour. Genetic similarities, which had been taken to explain physical similarities among relatives and to explain the recurrence of certain illnesses in families, are viewed in a much more problematic way to be the basis of complex behavioural traits such as ‘shyness, alcoholism or criminality’ (Fausto-Sterling 1992: 62) and, crucially for our purposes, behavioural differences between men and women. Sociobiology assumed sexual differences have evolved through natural selection to the maximal advantages of both sexes. It is important to be clear exactly what this programme requires – namely, that patterns of behaviour, supposedly empirically observed now, are of adaptive value.
Ideally, to show that a behaviour is an evolutionary adaptation, researchers must demonstrate that (1) the behaviour is heritable, (2) there is or was behavioural variability among individuals in a population, and (3) that differential reproduction, caused by the presence of the behaviour in question, led to an increase in the frequency of individuals tending to exhibit that behaviour in a population. Since researchers cannot go back in time to directly observe the evolution of current behaviours, they most often rely on indirect evidence. (Fehr 2011)
This has the consequence that hypotheses are invented for the supposed adaptive advantage of currently observed patterns of behaviour at some supposed earlier time in our evolutionary history. As many biologists, feminist and otherwise, have pointed out, this amounts to little more than the invention of Just So stories.
For example, Thornhill and Palmer in their book, A Natural History of Rape (2000), argue that rape is either a by-product of male adaptations to desire multiple sexual partners, or an evolutionary adaptation itself. In the adaptation view, rape is a facultative reproductive strategy, meaning that rape is the result of natural selection favouring men who commit rape when its evolutionary benefits in terms of producing offspring outweigh its evolutionary costs. (Ibid.)
There has been significant criticism of such stories (Travis 2003). For example, Elisabeth Lloyd (2003) highlights not only the complete lack of evidence that rape is of adaptive value but also the assumption that rape has a unitary meaning across historical times and cultures.
At the more general level, there is scepticism that complex social behaviour could simply be programmed in. This is especially the case since the patterns of behaviour that would maximize the chances of genes surviving are highly contextual. They depend on the environment in which the organism is placed, and in the case of human societies there is simply no continuity of environment. Moreover, it has been argued that such pictures misunderstand the way in which genes work: ‘a proper understanding of brain development suggests that while genetic information plays a key role in the unfolding of many details of the brain’s structure, extensive development of nervous connections occurs after birth, influenced profoundly by individual experience’ (Fausto-Sterling 1992: 77); ‘complex traits arise not simply (from genetic information) but also from the intrusion from the external environment and chance variations in development’ (ibid.: 88). We will return to this point. But what seems clear is that it is just not possible simply to read off complex patterns of behaviour from genetic modifications.
In the developments which evolutionary psychologists have made to sociobiological theories, psychological mechanisms are added into the picture. Human behaviours are not directly selected but, rather, are the product of psychological mechanisms that were selected. These mechanisms are ‘hardwired’ into the brain. This, if anything, has simply widened the range of behaviour for which evolutionary explanations are offered. Behaviours which did not exist in prehistoric times can now be explained as the outcome of a mechanism that was selected at that earlier point. So, we find bizarre examples. In the 2007 Journal of Social Psychology Peter Jonason argues: ‘Researchers have found that men and women pursue sex-appropriate strategies to attract mates. On the basis of intrasexual competition, men should be more likely to enact behaviours to look larger, whereas women should be more likely to enact behaviours to look smaller.’ (We might ask why, but he does not.) This, he claims, explains why, on undertaking exercise regimes, ‘male participants focus their energy on gaining muscle mass and enhancing their upper body definition, whereas female participants focused their energy on losing weight with emphasis on their lower body’ (Jonason 2007: 12). Here the Just So element of the suggestion seems evident. As Deborah Cameron remarks regarding many of the claims of this sort: ‘the only evidence for historic sex differences is the modern sex differences it is meant to explain’ (Cameron 2007: 112).
Such evolutionary stories, stories attempting to ground social behaviour in mechanisms of adaptive development, are supposedly reinforced by animal studies showing that male/female differences are found in non-human societies in ways that supposedly parallel those found in human ones. One study (Alexander and Hines 2002) that has gained much attention was one where toys which we might think of as ‘male’ and ‘female’ (trucks, cooking pans, dolls, stuffed animals) were given to vervet monkeys, and, it was argued, differences between preferences of human boys and girls were also found in the preferences of the male and female monkeys. This, it was suggested, indicated that these preferences were anchored in brain mechanisms which were shared across species. This study was repeated six years later with rhesus monkeys, with some similar and some different results. In Fine’s summary: ‘male
