Testosterone Rex
Page 8
By now it should be obvious that it’s pointless trying to work out whether feminism reveals women’s real sexually assertive nature, or is a social aberration that obscures their natural submissiveness. As Carol Tavris argues in her classic book The Mismeasure of Woman, “the idea that we have only to peel away the veneer of culture, the veneer of learning and habit, the veneer of fantasy, and the true sexual being will emerge” is profoundly mistaken.
Our sexuality is body, culture, age, learning, habit, fantasies, worries, passions, and the relationships in which all these elements combine. That’s why sexuality can change with age, partner, experience, emotions, and sense of perspective.57
This insight applies equally to the sexuality of men. It’s worth pointing out that everyone, including Evolutionary Psychologists, recognize overlap in men’s and women’s sexual preferences and behaviour, and that these are responsive to social and environmental conditions. But once we stop trying to extract men’s true sexual nature from the complicated social, economic, and cultural web in which every boy and man is embedded, the many hundreds of children begotten in Ismaïl the Bloodthirsty’s vast and brutally guarded harem starts to look less like a manifestation of uncompromised, evolutionarily honed male sexual nature, and more a symptom of the fact that Mr. Bloodthirsty was a despotic asshole. In an article titled “The Ape That Thought It Was a Peacock,” psychologists Steve Stewart-Williams and Andrew Thomas make the point nicely: “Does the behavior of these despots reveal the untrammeled desires of men in general, or does it just reveal the untrammeled desires of the kinds of men who become despots?”58
The ape that mistook itself for a peacock should also not forget that it’s human.
PART TWO
PRESENT
CHAPTER 4
WHY CAN’T A WOMAN BE MORE LIKE A MAN?
The belief is all but universal that men and women as contrasting groups display characteristic sex differences in their behavior, and that these differences are so deep seated and pervasive as to lend distinctive character to the entire personality.
— LEWIS TERMAN AND CATHERINE MILES, Sex and Personality1
Men and women belong to different genders which are truly disparate.
— CLOTAIRE RAPAILLE AND ANDRÉS ROEMER, Move Up2
IN HER REVIEW OF WELL-KNOWN BIOLOGIST LEWIS WOLPERT’S recent book Why Can’t a Woman Be More Like a Man? The Evolution of Sex and Gender,3 psychiatrist and journalist Patricia Casey conveys profound relief at the challenge the book poses to the politically correct views of gender theorists. After briefly touring a litany of “naturally occurring differences hardwired into our genes,” she concludes that the “obvious rejoinder” to Henry Higgins’s famous question in My Fair Lady, “Why can’t a woman be more like a man?” is “Because we aren’t and we never will be.”4 This, apparently, is the only sensible conclusion to reach. After all, “the argument that testosterone and the Y chromosome have no influence on how we think and feel defies credibility.”5
The assumption that, of necessity, these two biological agents of sex create not just a male reproductive system, but a distinctively male psyche, is in perfect keeping with the old view of sexual selection, whereby there’s usually a strong and predictable link between being a prolific producer of cheap sperm, and a characteristically male way of comporting oneself. But as the previous section showed, even in nonhuman animals biological sex doesn’t necessarily determine sexual nature, and especially not in ourselves. The biological realities of reproduction are never irrelevant, but even for dung beetles and hedge sparrows, other factors can have radical effects even on behaviour directly related to mating and reproductive success. These examples point to the surprising conclusion that biological sex may not be the fixed, polarizing force we often assume it to be.
In fact, even scientific understanding of sex determination (that is, how we come to be male or female) has shifted away from this view. According to the older, still prevalent, account, “The presence of a Y chromosome makes the embryo develop as a male; in its absence, the default development is along the female pathway,” as Wolpert summarizes the process whereby sex is determined. The “key gene”6 in this story is SRY, located on the Y chromosome. Individuals with the Y chromosome develop testes; in the absence of the Y chromosome, ovaries develop. The newly formed testes then produce high levels of androgens, particularly testosterone, which direct the development of male internal and external genitals; otherwise, female versions develop.
In this understanding of how maleness and femaleness come about, “The binary is stark: XX is female and XY is male,”7 as Harvard University’s Sarah Richardson observes. Reinforcing this cleanly binary view of sex is the apparently obvious state of the world. Even gender theorists, who unmoor themselves daily from reality as they grapple with the dizzying possibilities for reconstructing masculinity and femininity, agree that whatever genitalia you had when you put on your underwear in the morning, they will still be there when you get undressed again at night. About 98–99 per cent of the population either have XY chromosomes and male genitals (testes, a prostate, seminal vesicles, and a penis) or they have XX chromosomes and female genitals (ovaries, fallopian tubes, a vagina, labia, and a clitoris).8 Tel Aviv University neuroscientist Daphna Joel refers to the three core markers of maleness and femaleness as genetic-gonadalgenitals sex: or 3G sex, for short.9
But this account, in which a person’s sex hinges on the presence or absence of the almighty Y chromosome, turns out to be too simple. Consider, for instance, those few people in a hundred whose genes, gonads, and genitals don’t all neatly align on either the male or female side: people you surely know, but quite possibly without knowing that you do. Social conventions, policies, and laws that require everyone to be either male or female obscure the biological reality that an “either/or” binary view of sex works for most people, but not everyone. A small but significant proportion of the population are “intersex”: they are “like a female” in some aspects of 3G sex, but “like a male” in another, or are in between the male and female form in some aspect. For example, individuals with a male XY complement of chromosomes, but whose receptors don’t respond to the androgens that are critical for masculinizing the genitalia, develop male testes but female external genitalia. As the Intersex Society of North America points out, this means that, despite the Y chromosome, these women “have had much less ‘masculinization’ than the average… woman [with XX chromosomes] because their cells do not respond to androgens.”10 Or consider congenital adrenal hyperplasia (CAH), in which an unusually large amount of androgens are produced in utero. In girls, this can result in somewhat masculinized external genitalia.11
Drawing attention to examples like these back in the 1990s, Brown University biologist Anne Fausto-Sterling risked making people’s heads explode by observing that there are actually half a dozen or so sexes.12 In the heyday of acclaim for the SRY gene on the Y chromosome as the sex-determining gene, Fausto-Sterling pointed out that intersex individuals are awkward for a model that doesn’t allow for “the existence of intermediate states.”13 Following the neglected arguments of two geneticists, Eva Eicher and Linda Washburn, Fausto-Sterling suggested that deeply culturally embedded associations were implicitly at work in this scientific model: namely, “female,” “passive,” and “absence.” The development of testes from an “androgynous” gonad is an active, gene-directed process, but in the absence of the potent, male SRY gene, ovarian tissue just… happens, as the default?
Contemporary sex determination science now recognizes that female development is as active and complex a process as male development. And what has also become clear is that many genes are involved in sex determination: SRY on the Y chromosome; a few on the X chromosome (including some involved in male sexual development); and then, surprisingly, dozens of others located on other chromosomes.14 That’s why, if you see the phrase “sex chromosomes” in scare quotes, it’s not because some batty feminist scholar refuses to recognize t
he biological basis of sex, but because genetic sex isn’t located in a stark binary—Y present or absent—but is scattered about the genome. Sex determination is therefore “a complex process.” Rather than the simpler old scenario in which the SRY gene tips males onto a distinct developmental path, “the identity of the gonad emerges from a contest between two opposing networks of gene activity.”15
Of course, when Patricia Casey rhetorically asks why a woman can’t be more like a man, she doesn’t wonder why it is that a woman can’t turn her clitoris into a penis, or her ovaries into testes. Casey is expressing a common belief that sex—most prominently in the form of testosterone and the Y chromosome—has a fundamental effect on the brain and behaviour. As Penn State University psychologist Lynn Liben puts it:
Males and females are assumed to have different “essences” that, although largely invisible, are reflected in many predispositions and behaviors. These essences are given—at the individual level—by a range of genetic and hormonal processes and—at the species level—by evolution. They are viewed as part of the natural order, likely to be presumed to operate across contexts and across the lifespan, and often presumed to be immutable (at least in the absence of herculean and unnatural efforts to change them).16
But does it make sense to expect sex to create essences in the brain and behaviour? Across species, the same evolutionary problem of sexual reproduction has been solved in lots of different ways—and this means that possession or absence of a Y chromosome17 (and the other genetic components of sex) doesn’t, in and of itself, dictate a particular way of behaving. But also, within some species—including our own, as this chapter fleshes out some more—neither sex has the monopoly on characteristics like competitiveness, promiscuity, choosiness, and parental care. The particular pattern, as we saw, depends on the animal’s ecological, material, and social situation. This suggests that, even within a particular species, the effect of the genetic and hormonal facets of sex on brain and behaviour must not inflexibly inscribe or “hard-wire” particular behavioural profiles or predispositions into the brain; not even those more common in one sex than the other. Instead, they are drawn out to a greater or lesser degree, as circumstances dictate.
The sexes’ reproductive roles (as in who produces which gametes, and puts what organ where) are distinct in a way that behavioural roles are not. Presumably this is because there is no environment or context in which having an intermediate version of the reproductive system, or putting together different parts of it in creative new ways—like a penis with a uterus, or testes with a set of fallopian tubes—would have been beneficial for reproductive success. Not so, though, for behaviour. None of which is to say that sex doesn’t influence us above the collar. But should we expect the genetic and hormonal components of sex to have the same kind of effect on the brain and behaviour as they do on the reproductive system? With even that developmental process described by one expert as “a balance” rather than a binary system,18 we might start to wonder not just whether, but why, sex should produce male and female brains, and male and female natures.
SEX CATEGORIES ARE THE PRIMARY way that we carve up the social world. It’s the first thing we want to know when a newborn enters the world. It’s often what we register first and fastest when we meet someone. We state it on almost every form we fill out. In most countries, we’re legally required to be one or the other. We mark and emphasize it with pronouns, names, titles, fashion, and hairstyles.19
We probably wouldn’t do this if maleness and femaleness—3G sex—didn’t have certain important features. If last week you were female and had ovaries, a vagina, and so on, but this week you are male and have testes and a penis, those M and F check boxes probably wouldn’t be nearly as common. If most of us were intersex in some way or another, the ubiquitous question, “Is it a boy or a girl?” wouldn’t be so compelling. And if the shape of our external genitalia fell on a continuum, with the majority of people in an ambiguous midrange shape, it’s an interesting question whether our sex would play such a key role in how we present ourselves to the world.
But of course 3G sex is not like this. The genetic and hormonal processes of sex, despite being complex and multifaceted, usually create distinct, consistent, and stable 3G sex categories. It’s perhaps understandable for people to assume that sex has the same kind of fundamental effect on the brain as it does on the genitals. As Joel and a colleague put it, we assume that “sex similarly acts serially and uniformly, exerting an overriding and diverging effect, ultimately leading to the creation of two distinct systems, a ‘male’ brain and a ‘female’ brain.”20 It’s not uncommon, in what passes for debate on Twitter, for people to counter the claim that there is no such thing as a “male brain” and a “female brain” by linking to a scientific article reporting a sex difference in the brain. In other words, as soon as we learn that brains differ according to sex, the implicit reasoning is that the brain must therefore also have a sex and, like the genitals, create female and male categories.
In fact, the classical scientific view proposed something along these lines. As with the genitals, testosterone was thought to be a key player, the prenatal gush produced by the newly formed testes masculinizing and defeminizing the brains of males in broad-brush fashion, while in its absence the brain is feminized. In this way, “genetic sex determines gonadal sex and gonadal hormones determine brain sex,” as leading researchers Margaret McCarthy and Arthur Arnold neatly summarize it.21 Scientists involved in non-human animal research assumed that these sex effects create discrete male and female neural circuits restricted to those involved in mating. But of course, for many psychologists and popular writers discussing the human condition, “mating behaviour” potentially includes in its scope just about every aspect of human psychology—from a visual system attuned to babies’ faces, to a sense of humour that showcases one’s superior reproductive potential.22
However, new evidence reveals a far more complicated picture, as McCarthy and Arnold explain. Sex isn’t a biological dictator that sends gonadal hormones hurtling through the brain, uniformly masculinizing male brains, monotonously feminizing female brains. Sexual differentiation of the brain turns out to be an untidily interactive process, in which multiple factors—genetic, hormonal, environmental, and epigenetic (that is, stable changes in the “turning on and off” of genes)—all act and interact to affect how sex shapes the entire brain. And just to make things even more complicated, in different parts of the brain, these various factors interact and influence one another in different ways.23
For example, as Joel points out, environmental factors (like prenatal and postnatal stress, drug exposure, rearing conditions, or maternal deprivation) interact with sex in the brain in complicated and non-uniform ways.24 Take just one study, showing that lab rats that have enjoyed a peaceful, stress-free life show a sex difference in the density of the “top-end” dendritic spines (these transmit electrical signals to the neuron cell body) in one tiny spot of the hippocampus. (The female dendritic spines are denser.) But look at the same brain region in a group of rats that have been stressed for just fifteen minutes, and now the dendritic spines of the male rats are bushy, like those of unstressed female rats. Conversely, the top-end dendritic spines of stressed female rats become less dense, like those of unstressed male rats. In other words, brief stress exposure reverses the “sex difference” for that particular brain characteristic.25
And it gets even more complicated than this. A particular environmental factor can have a profound effect on sex differences for one brain characteristic, but the opposite influence, or none, for others. For example, brief stress has a different effect on the “bottom-end” dendrites in this same brain region. Here, male and female dendritic spines are identical, so long as those rats have lived a stress-free life. But what happens if the rats are stressed? There’s no effect on bottom-end dendritic spines in females, but their density increases in males. So what we have is a situation in which sparse top- and bottom-end
dendritic spines are what you tend to see in non-stressed males and stressed females, bushy dendritic spines top and bottom is what you see in stressed males, and bushy tops with sparse bottoms is what you expect of non-stressed females.26
Confusing? That, in a way, is the point. You might also be beginning to wonder what exactly is the “male” pattern of dendritic spines? What is the “female” version? Unless you have very strong opinions on whether the true way of life for a laboratory rat is one of complete serenity, or whether it is the right and proper fate for every rat to experience brief episodes of high tension, there isn’t really a good answer to this question. (For this reason, Joel recommends avoiding using the terms “male form” and “female form” to refer to brain characteristics.)
This particular study, conducted by neuroscientist Tracey Shors and colleagues, looked at one simple environmental effect on two extremely precise brain characteristics in one tiny part of the brain. Now imagine hundreds of these interactions between sex and environment, affecting many different features of the brain, as wild rats experience their own unique and rich tapestry of life. With each experience, some brain features change their form, others will not, giving rise to unique combinations of forms. What we should expect to emerge, then, from this “multiplicity of mechanisms”27 is not a “male brain,” or a “female brain,” but a shifting “mosaic” of features, “some more common in females compared to males, some more common in males compared to females, and some common in both females and males,” as Joel and colleagues conclude.28