A second important consequence of our inefficient sexual practices is the disruption to the supposedly universal principle that males’ freedom from the labours of gestation, birth, and lactation should nudge them hard towards Maserati-driving, lady-magnetizing, baby-abandoning traits. Supposedly, it’s the economics of reproduction that drives men, more than women, to succeed and sleep around, but it’s easy to get too carried away in estimates of men’s likely return on investment. In reality, in the absence of ecological, social, economic, and legal conditions that allow for harems, a man has to put in a hell of a lot of legwork to out-reproduce the steadfast husband and father. So why should we expect the reproductive potential of a tiny subset of men in a few pockets of history to be the foundation of a male essence—for there to be an incipient Genghis Khan in the sexuality and strivings of every male?
This diversity of possibilities for men illustrates the uniquely tricky developmental problem we humans have had to solve: “A newborn human must be ready to join any cultural group on Earth, and without knowing which,” as evolutionary biologist Mark Pagel puts it.16 And our genes don’t know in advance what that cultural group’s consensus will be on the appropriate roles for men and women. A baby girl could potentially be born into a society that expects her to play piano and embroider, study at a university, walk dozens of miles a day to fetch water, plant crops, tend animals, prepare animal skins, or hunt animals—and to grow up to live a life of chaste wedded monogamy, or to have two or three husbands simultaneously. For a baby boy, his destiny might involve crafting musical instruments, butchery, making nets, milking, pottery, investment banking, or intensive child care—and his future wife could be a thirteen-year-old girl or a thirty-year-old professional. Some kinds of future roles are more likely than others across societies, certainly, but all are possibilities.17 And, regardless of our biological sex, life will likely demand we all, at some point, cherish and care for others; take risks; and compete for status, resources, and lovers.
Why, then, should we expect sexual selection to have fixed in our genes the recipe for a “female brain” and a “male brain” that creates distinct female natures and male natures, respectively? Certainly, the various genetic and hormonal facets of biological sex have to coordinate in ways that are (mostly) reliably directive when it comes to the reproductive system. But beyond the genitals, it would be useful for sex to be somewhat noncommittal, to play it by ear in its effects on brain and behaviour, to be pliant to the many other developmental resources it takes to build a person.
In other words, the developmental puzzle is not the one that Testosterone Rex so compellingly solves for us—how sex creates males who, beneath the cultural veneer, are timelessly, universally, and immutably like this; females like that. The real problem is how sex (usually) creates essentially different reproductive systems, while allowing the differences in men’s and women’s behaviour to be non-essential: overlapping and mosaic, instead of categorically different; conditional on context, not fixed; diverse, rather than uniform.
Some of the progress in working out how we achieve this neat trick comes from a major scientific shift, as we saw in the second part of the book. It has always seemed natural to ask: “How does this sex difference in the brain or hormones make females and males behave, think, or act differently?” That’s the only question to ask when you’re solving the red herring problem that Testosterone Rex explains. But a no less important question is how males and females can so often behave similarly, despite biological differences. When we notice that girls and women sometimes take risks and compete to the same degree as boys and men, when we realize that people have idiosyncratic mixes of “masculine” and “feminine” brain characteristics and gendered qualities, it becomes clear that biological sex can’t have nearly as potent an effect on male and female behaviour as it does on male and female anatomy. And when we no longer assume that sex differences add up, and up, and up, we start to ask whether some sex differences are compensating for others, to make the sexes similar, not different.
A second scientific change is also helping to explain how sex can be such a helpfully light-handed and flexible influence in human development: a growing interest in how gender affects sex-linked factors, like testosterone. As Anne Fausto-Sterling advises, “think developmentally. Remember that living bodies are dynamic systems that develop and change in response to their social and historical contexts.”18 Testosterone changes bodies as well as brains, for instance, meaning that even when you measure a person’s digit ratio, you don’t just capture the effects of “sex,” but potentially the cumulative effect of that person’s more (or less) masculine appearance being responded to by others through a gendered lens. Nor do circulating T levels reflect pure sex. As we saw in Chapter 6, social context, experience, and subjective meaning can alter T levels—as well as override testosterone’s influence on behaviour, or compensate for its absence. These often-gendered phenomena are a human specialty that, when we have the will to do so, we have a uniquely powerful capacity to change.
These gender constructions are a core part of our developmental system, bringing us to the final key to understanding the complex interrelations among sex, gender, and society. As we saw in Chapter 4, in animals, the developmental system—that legacy of place, parents, peers, and so on that every individual reliably inherits along with his or her genes—plays a crucial role in the development of adaptive behaviours.19 In this regard, we are both like, and unlike, other animals. Our “complex and varied culture… resembles animal cultural traditions about as much as a Bach cantata resembles a gorilla beating on its chest,” as Pagel observes.20 Some evolutionary scientists argue that this uniquely human feature of our own developmental system is what makes our dazzling diversity of ways of life possible, in concert with another special, key human characteristic. This is an adaptation to learn from others in our social group. From the tender age of just two, we conform to the behaviour of our peers—notably, even other great apes don’t “ape” each other in this way.21 In particular, we’re geared towards learning from those who are prestigious, successful, or similar to us in some important regard, with whom we come to identify, and from whom we learn, internalize, and gain our understanding of cultural norms.22 Gender constructions penetrate just about every aspect of this cultural legacy. They aren’t some dubious concept made up by gender scholars who don’t believe in biology and evolution: they are part of both. Every newborn human inherits gender constructions as an obligatory part of their developmental system: gender stereotypes, ideology, roles, norms, and hierarchy are passed on via parents, peers, teachers, clothing, language, media, role models, organizations, schools, institutions, social inequalities… and, of course, toys.23
The T-Rex view of “boy toys” and “girl toys” is familiar from earlier in the chapter: the pink and blue categories reflect the preferences of “female brains” and “male brains” made distinctively different, in large part by the hand of testosterone. By way of evidence for this view, defenders of gendered toy marketing often refer to the more masculine preferences of girls with congenital adrenal hyperplasia (CAH). (As you might recall from Chapter 4, CAH is a condition in which very high levels of androgens are produced in utero.) And from here, it’s just a few short steps to the conclusion that sex inequality is natural and inevitable. But since Testosterone Rex is extinct, we need another explanation of what’s going on.
In the first year of life, baby boys and girls provide little in the way of evidence that their brains are tuned to different radio stations of life. For example, at birth, girls and boys are pretty similar overall in how interesting they find a face versus a mobile. Although a Cambridge University study found a statistically significant difference between the sexes,24 even if you overlook important flaws in the method of this much-publicized study,25 the differences are underwhelming. (Boys looked at the face 46 per cent of the time; girls, 49 per cent; boys looked at the mobile for 52 per cent of the time; girls, 41 per cent.) F
our to five months later (according to a better controlled study), both boys and girls prefer to look at people than at objects, to the same degree.26 In the second year of life differences do seem to emerge, but they are still rather subtle. A large recent study of nearly one hundred two-year-old children measured how long they played with a doll and a truck (among other toys), and how often they nurtured or manipulated the toys. About a third of the time a randomly chosen boy would play in a more “girlish” (or non-“boyish”) way than a randomly chosen girl, both in terms of what toy they played with, and how they played with it.27 And sometimes at this age kids play as long, or longer, with counter-stereotypical toys than with those that are supposedly “for them”: like the fourteen-month-old boys in one study who played for about twice as long with a tea set as they did with a truck, a train, and motorcycles, put together (while the girls in this study spent as long with these “boy toys” as they did with dolls).28
So how do we get from this to the more markedly stereotypical toy preferences children come to develop? In keeping with the suggestions of cultural evolutionists, developmental psychologists describe young children as “gender detectives.”29 Children see that the category of sex is the primary way that we carve up the social world, and are driven to learn what it means to be male or female. Then once they come to understand their own sex, at about two to three years of age, this information takes on a motivational element: kids begin to “self-socialize” (sometimes to the chagrin of feminist parents). Presumably not coincidentally, this is the time period during which many boys start to shun pink, and many girls become especially drawn to it.30 By just three years of age, when children are presented with other kids endorsing novel, gender-neutral objects and activities, they show “robust preferences” for those promoted by kids of the same sex.31
In fact, a recent study led by Cambridge University psychologist Melissa Hines suggests that at least part of the reason that girls with CAH have more boyish play interests is because they’re less influenced by gender labels and gender modelling than are other children.32 Four- to eleven-year-old matched control girls (and boys with and without CAH) preferred a gender-neutral toy that was presented either explicitly or implicitly as being “for them” (echoing findings from the 1970s and 1980s).33 By contrast, girls with CAH were impervious to information that particular toys (like a xylophone or balloon) were “for girls,” despite remembering that information just as well. This makes sense, given the somewhat weaker female gender identity of this population.34 In my previous book, Delusions of Gender, I pointed out that studies of girls with CAH are done in ways that leave open the possibility that these girls aren’t, in fact, drawn to some unidentified quality intrinsic to “boy toys” that appeals to their “masculinized” brains, but simply identify more than do girls without the condition to masculine activities, whatever those might be in a particular time, place, and culture.35 Along similar lines, Barnard College sociomedical scientist Rebecca Jordan-Young points out that to understand these girls’ more masculine preferences, we have to consider the psychosexual effects of the condition: girls are born with atypical or masculinized genitalia, they often undergo intensive medical and psychiatric observation or intervention, and have physical characteristics out of keeping with cultural ideals of feminine attractiveness.36
Certainly, as with novel and gender-neutral objects, children’s interest in even counter-stereotypical toys can be piqued by seeing a child of the same sex play with it.37 And more recent evidence points to the influence of the now-ubiquitous colour coding of gender. Psychologist Wang Wong, together with Melissa Hines, compared how long boys and girls played with a train and a doll, first when they were twenty to forty months old, and then again about half a year later.38 At both ages, it’s worth pointing out, girls played longer with the train than with the doll. (Draw whatever conclusions you will regarding the implications for the “naturalness” of child care as an occupation for women, compared with the much better remunerated occupation of mechanical engineer.) But the researchers’ main interest was in whether children were influenced by the colour of the toys. Lo and behold, sex differences in toy preferences were smaller when children were presented with a pink train and a blue doll than when presented with the same toys in stereotypical colours. In fact, at the slightly older age, the same boys and girls showed moderate to large differences in the amount of time they spent playing with a blue train and a pink doll, but small and statistically indistinguishable amounts of time playing with a pink train and a blue doll.39 Whatever role, if any, testosterone or other facets of biological sex play in girls’ and boys’ initial overlapping toy preferences (and there are other possible explanations), all of this is troublesome for the Testosterone Rex perspective. One doesn’t expect a deeply biologically rooted, evolved sex-specific nature to be so contradictory and inconsistent in its expression, or to be so easily overridden by a quick paint job.
From birth, children encounter endless gender clues and hints in the real world: gender stereotypes transmitted in advertisements; encouraging or discouraging words, expressions, or body language from others; toy stores and packaging; movies; TV shows; the sex-segregation of adult social roles; and so on. Of course, these many influences don’t impose themselves onto a blank slate: every child is different, with their own internal inclinations and understandings. Some influences will leave particular children untouched while affecting others. (Interestingly, it may be that children who have a stronger “lens of gender” may be especially susceptible to the influence of stereotypical information.)40 Some gender messages will push in opposite directions, and no single influence is likely to be very large. But they accumulate. And they provide a potential explanation for how robust sex differences in toy preferences develop around the age that children develop a firm understanding of which side of the critical social divide of gender they belong. The gendered developmental system has achieved what prenatal testosterone can’t.
This conclusion, by the way, is perfectly consistent with claims that back in our evolutionary past it was adaptive for women and men to have had very different roles: for women to care for children, and for men to handle spears and kill stuff. It’s compatible with this being a common pattern across societies. And it’s also perfectly reconcilable with things being very different now, and different again in the future.
As Paul Griffiths explains, it’s well accepted in evolutionary biology that even adaptive traits that increase reproductive success can take different forms, depending on environmental conditions.41 (Evolutionary Psychology, for instance, famously describes this in terms of a jukebox metaphor: various possible behavioural “tunes” are built into the genes, and which one gets “played” depends on circumstances.)42 Just ask your nearest dung beetle. The male cichlid fish of Chapter 6 provide another striking and more dynamic example. Whether a male develops into a dominant fish—physically, behaviourally, and hormonally—depends on his social situation and real estate conditions. A fish placed in a tank with a smaller fish will become dominant, a fish without a breeding territory will remain subordinate, and hormones follow status. Or recall the female bush crickets from Chapter 1 that compete for males bearing nutrient-rich sperm packages when times are bad, but sit back and choose when the living is easy. Then there were the hedge sparrows, that allow the wildly variable sexual mores of their mating system to be set by, among other factors, the happenstance of the location of their breeding territories. These animals certainly seem to be behaving adaptively, but that behaviour clearly isn’t fixed by their genes or nature. What we can conclude from these examples is that just because a particular kind of behaviour is adaptive in certain conditions doesn’t mean it’s fixed and will develop regardless.
But what about adaptations that are standard issue, that we see in a species regardless of environmental or social circumstances? Wouldn’t these be locked into genetically inherited biology, to ensure they develop? Not necessarily. Recall the rat mothers of Chapter 4, t
hat especially vigorously lick the anogenital region of their male pups. This strange phenomenon illustrates that natural selection is a frugal process that can, and does, draw on stable and reliable inputs from the developmental system, beyond the genes. Griffiths has another nice example: the ability of rhesus macaque monkeys to recognize emotional expressions and successfully navigate conflict. The development of these skills, despite being obviously highly adaptive, turn out to depend on social contact and interactions in infancy. But that’s fine, because these are social experiences every young rhesus macaque monkey will reliably encounter in the normal course of events, generation after generation. As Griffiths points out, that rhesus macaques need a particular kind of early social input in order to develop these abilities “throw[s] no doubt whatever on the claim that these abilities in adult macaques are the result of adaptive evolution.”43 Indeed, in the rat case, the mother’s licking contributes to the development of something as fundamentally adaptive as sexual behaviour.
What does all of this mean for ourselves, given the monumental ecological, technological, social, medical, and cultural changes that have taken place throughout human history? As John Dupré points out:
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