Are Sex Differences Genetic?

Are men and women completely interchangeable? This is obviously an enormous subject, with many dimensions and nuances. One side in the debate, the care egalitarians, generally see biological differences as relatively unimportant and the big differences in behaviour as largely the product of social conditioning, reinforced by powerful norms, and therefore reformable. (This used to be the classical feminist position but in recent years there has been much more willingness to accept the reality of significant average differences, reinforced by feminism’s reinvigoration in the battle against the unconstrained rights of trans women.)

The care balancers, on the other hand, accept that differences are strongly reinforced by culture but argue that our different evolutionary roles have also bequeathed us some important innate differences. Women have babies and men don’t. Men are on average bigger and stronger than women. These two differences alone have a powerful influence on average behaviours.

Men and women have been under many of the same, but also many different, selection pressures over the course of history, and their bodies have evolved to do somewhat different things, as Caroline Criado Perez points out in her 2019 book Invisible Women: Exposing Data Bias in a World Designed for Men, a critique of a world designed for the male body. Men are typically more aggressive, more risk-taking and have a stronger sex drive than women. Men are a bit more interested in things and women in people. Sex differences in spatial intelligence are real, though not enormous.

All these things should not be controversial, especially when one introduces the important caveat that they are also ‘dimorphic’ differences, meaning different but overlapping, rather than binary. Think of two overlapping bell curves, side by side. Although men are on average more aggressive than women in aggregate, some individual women are more aggressive than some individual men. But also bear in mind that relatively modest average differences are often associated with much larger differences at the extremes. There are many more very aggressive men, who are disproportionately represented in prison and among domestic abusers, than very aggressive women.

Aggression differences are substantially driven by the hormone testosterone, which men have more of than women, as Harvard biologist Carole Hooven explains in her 2019 book Testosterone: The Story of the Hormone that Dominates and Divides Us. It is also well established that levels of testosterone and aggression track each other over a lifetime, with both spiking in young adulthood and then trailing away. She notes, too, that women who transition to ‘being men’ and who take testosterone as part of their transition report that they have higher sex drives and don’t cry as easily.

There are physiological differences everywhere in the body, including in the brain, which generally matures earlier in girls – one reason for the gender gap in education. And it is from these differences that some different behavioural traits arise. For example, two common female traits are higher levels of anxiety and greater agreeableness, and both are thought to stem from the basic one of women’s greater physical vulnerability.

The sex trade is another often-cited indicator of a big average difference, with around 99% of buyers of sex with strangers being men. This points to higher levels of socio-sexuality in men, meaning a desire for sexual variety and a greater ease of separating sex from emotional attachment.

In his discussion of sex differences in his book Of Boys and Men: Why the Modern Male Is Struggling, Why It Matters, and What to Do About It, Richard Reeves has a useful three-point list of how to think about these differences in an era of sex equality, embracing equality while acknowledging difference where relevant.

First, even if differences are innate (in the sense of arising from a physical difference), they can be magnified or muted by culture. And, indeed, the impact of sex differences on our comfortable, technology enhanced lives in the 21st century is diminishing: traditional masculine virtues such as physical courage and stoicism are less required in a mainly peaceful, post-industrial society, and women’s nurturing qualities count for less if they are not having children and are exercising a much wider range of emotions and aptitudes.

Second, many of the differences are only modest. On spatial intelligence, perhaps the most clearly established sex difference in all cognitive abilities, 70% of men are better than the average woman (meaning that 30% of men are worse than the average woman). Third, average differences should not colour our view of individuals. Even if women are on average hardwired to be more nurturing than men – as they are – that does not prevent my youngest son from being a caring primary school teacher, and there are some women I know with no interest in children at all.

What does all this mean? Bearing in mind that there are only trivial differences on some of the most important things, like IQ, it is nevertheless the case that masculine traits can be more useful in some contexts and female ones in others. (On IQ there are more men found at the tails of stupidity and genius, with women clustering more around the middle.)

It also implies that there are limits to how far sex differences can simply be ignored. Young women should certainly continue to be encouraged into STEM (science, technology, engineering and maths) jobs as there may well be cultural norms that cause underrepresentation, and also advantages in including women’s perspectives in those roles (given that girls do just as well if not better than boys in maths exams). However, that does not necessarily mean that a 50:50 balance is either possible or even desirable. The situation is similar for men moving into female-majority care jobs.

The same principle of openness to women should apply to all jobs requiring a high degree of typical male traits such as aggression and risk-taking. American feminist and Nobel prize-winning economist Claudia Goldin says that even though “there is lots of evidence that women on average take fewer risks and are less pushy” than men, there are more women who are now competitive in high-risk financial market type jobs.

Reasonable people will disagree about when the barriers to equality have been sufficiently removed. In the UK, even when girls get good A-level grades in maths and physics, they are still much less likely than boys to study them at university, while young women are hugely over-represented in the ‘caring’ sciences: almost two thirds of medical students are now women, almost all veterinary students and about 80% of psychology students.

The so-called gender equality paradox reinforces this point. The paradox states that in societies with deep gender equality norms, especially Nordic countries like Sweden, women are more likely to choose caring professions and less likely to be well represented in STEM disciplines. Highly patriarchal countries like Algeria, Tunisia and Turkey have a higher percentage of female STEM graduates (around 40%) than the Nordic countries (25% or less).

A famous paper by Gijsbert Stoet and David Geary found that looking at test scores across 67 countries girls performed just as well in science as boys, but in relative performance boys performed better in science overall compared with other subjects whereas girls were even stronger in their other subjects. Stoet and Geary argue that countries that empower women also empower them to pick whatever career they will enjoy most and perform best in.

The Stoet/Geary paper and, indeed, the idea that low STEM representation is an expression of women’s true preferences, has not gone unchallenged. Critics argue that gender norms remain strong even in egalitarian places like Sweden and that bright young women in poorer countries are more motivated to maximise income on behalf of families and hence choose higher-paying STEM careers.

But in Sweden there is sharp gender segregation not only in STEM versus care professions but also in the private sector, which is heavily male, versus the public sector, which is 75% female. The story is similar in other Nordic countries. By 2035 only six out of 35 Swedish professions are expected to be gender balanced. Swedish politics, at most levels, has an almost equal representation of men and women, but in leadership positions in the private sector women are much rarer. The US has a much higher share of female senior managers (43%) than the Nordic countries (31%).

Claudia Goldin, who is also one of the leading researchers of persistent labour market disadvantage for women, reckons that only about 20% of the residual pay gap is down to discrimination, with most of it based on women’s choices, reflecting the fact that they often choose jobs and careers that are better suited to combining with motherhood (part-time or easier to travel to) or offer more intrinsic satisfaction but lower pay.

In any case, this evidence supports a less dogmatic care balancer approach to the gender division of labour. What matters is not whether different choices are driven by innate differences or socialisation but the democratic honouring of people’s actual expressed preferences. No choices are completely free from social norms, but choices are not delegitimised simply because they are always constrained in some way. The alternative is a kind of Leninist assumption that care egalitarian policymakers know your true interests better than you do.

Moreover, there is a tension in the justifications for equal representation. Is it because men and women are the same, or is it because they are different? Is it that sex differences are irrelevant for almost all human functions so equal representation should be the natural state of affairs in a world without discrimination? Or, on the contrary, is it that women have a distinctively different perspective that is needed from the boardroom to the battlefield?

Both of these equality claims can be true in different contexts. But in other contexts neither of them are convincing and a gender divide still makes some sense. No one is campaigning for a gender balance among refuse collectors or prisoners. Likewise, there is no distinctively female approach to quantity surveying or nuclear engineering.

Gender roles, based on sex differences, have evidently become more elastic in recent decades, but they still exist. Most people experience them as positive things, as welcome parts of their identity. Some people at the most atypical end of their sex’s common characteristics are more likely to feel them as oppressive, most notoriously in the case of those who wish to transition. But this reinforces the case for flexibility in the way that gender roles are perceived, not for pretending they don’t (or shouldn’t) exist.

Sociologist Catherine Hakim describes three types of women in modern Britain — the work-centred (20%), the home-centred (20%) and the adaptive (60%), meaning those who wish to combine the two but when children are young and prefer to work part-time or not at all for a few years. The three groups have different priorities, and probably different views of how to be a woman, but they have all benefited from greater opportunities and the shift in the balance of power and authority.

Patriarchy in the technical anthropological sense, meaning male control over women’s fertility and sexual behaviour, has not existed in a country like the UK for many generations. And in the more everyday sense of men having more power than women in the public sphere, we are probably in a transitional phase out of patriarchy.

Finnish demographer Anna Rotkirch describes this transition:

Traditional patriarchal societies are characterised by early and universal marriage, early and high fertility, and deference of the younger generations to the older generations and of women to men. … More liberal and individualised societies have later and lower rates of marriage, later and lower fertility, more equality between both the generations and the two sexes, and much greater leeway for individual sexual behaviours and gender identities. These changes in power relations… shape the lives of many contemporary couples.

Is it appropriate to talk about a shifting balance of power between men and women? Maybe a tangled dance of love and conflict, dependence and autonomy, is closer to the perplexing reality. Conservative feminist writer Louise Perry argues that because women (on average) are weaker and temperamentally more agreeable than men, there will always be a need for a women’s movement to protect their interests. After all, the most brutal form of power of men over women is evident in the murder and rape statistics. But Perry also says that even before the big increase in female presence in the public realm in recent decades women have always wielded a kind of parallel power in the domestic realm. As one guest on her podcast put it: “Was your grandmother really powerless?”

As a young reporter on the York Evening Press in the early 1980s, one of my favourite jobs was interviewing older couples for the golden wedding anniversary page. These couples had married in the early 1930s, a few years after women had achieved political equality, and it was fascinating hearing their stories of courtship in the Depression years and then, often, wartime separation when children were young.

They lived in an era of very different public gender norms and more constrained opportunities for ordinary women, but in most cases it was the woman who spoke for the couple and more often than not seemed the dominant (and certainly the most articulate) figure in the household. That may have been partly because the men, by then in their mid 70s, were often the physically weaker of the two. But abstract questions of gender power, while not irrelevant, seemed too crude to apply to such couples; they invariably agreed, in response to my stock question, that the secret of a long marriage was ‘give and take on both sides’.

Power or authority or agency in the private realm is rarely taken into account in discussions of gender power, maybe partly because it is harder to quantify than, say, the number of women in Parliament (now up to 40%) or FTSE 100 boardrooms. But after the initial surge of women into positions of power in the professional world in recent decades, the next wave can, perhaps, weigh up the options more objectively and appreciate that what often accompanies the under-esteeming of the domestic realm is the over-esteeming of the workplace.

Eliza Filby runs regular focus groups and finds that young women in their 20s, Generation Z, are increasingly shunning the committed career paths that their professional mothers took.

And here is Jess Butcher, a tech entrepreneur in her early 40s, speaking in a TED Talk:

I am seeing a number of the highest professional flyers in my circle quietly ‘leaning out’ of ambitions of ‘making partner’… so as not to miss out on those precious early years of family life. Two years ago after losing two close friends to cancer I realised too that if I wasn’t careful I was going to miss those early years too, years I will never get back. So I made the decision to step back from the day-to-day-running of my business.

Why does this seem an unusual, even countercultural thing to do? It is partly because most of the women who have dominated the public conversation about what women want are strongly public realm-orientated. Here is Joeli Brearley, founder of lobby group Pregnant Then Screwed: “Maternity leave can be desperately, achingly lonely. … And at times being stuck at home with a tiny baby who needs you 24/7 can feel like staring straight into despair.” She cites a Pregnant Then Screwed survey that found 19% of mothers wish they had gone back to work earlier, a proportion roughly coinciding with Catherine Hakim’s work-focused women. This is an attitude that many male politicians can easily identify with.

But Louise Perry again: “Women with more masculine temperaments, women who are less inclined to have children, who are less agreeable and so on, are more likely to end up in senior positions in politics. And there is, therefore, a tendency to assume that this is a universal tendency among women and to make decisions accordingly. But it isn’t.” Many of the most successful female politicians are childless, as are about half of female academics.

Many women, in the words of podcaster Chris Williamson, have been encouraged to “work like your father and have sex like your brother”. This tendency of the dominant strand of feminism to promote more traditionally masculine traits like aggression and competitiveness and to downplay traditionally female traits such as nurture and agreeableness has been noted by many feminist writers including Ruby Warrington and Camille Paglia. It seems to suit some women, but not all.

Perry now also regrets the libertarian turn that feminism took in the 1970s and sees aspects of the sexual revolution as regressive. The arrival of the pill in the 1960s, as a safe and secure way for women to control their own fertility, was, at the time, seen as a great step forward. It led to a big expansion in female professional employment, especially in the US, as college-educated women began to push back their age of marriage (which was still 23 in 1960) and could establish themselves in careers before marrying and having children.

However, as author Mary Eberstadt has pointed out, the pill also made pregnancy a woman’s responsibility rather than a joint responsibility. The old norms (that generally disapproved of sex separated from long-term commitment) existed in part to protect women from the risk asymmetry in sexual intercourse – the fact that it has much bigger potential consequences for a woman than a man – and locked in men, via the shotgun wedding, to mutual responsibility if a child was conceived.

After the pill, and as part of the wider idea that obstacles to sexual pleasure belonged to a repressive ancien régime, the norms were turned upside down. As women became, potentially, always available for consequence-free sex, so long as the principle of consent was respected, it reduced their bargaining power in the mating game. It also led to an increase in both abortion – around 30% of conceptions in the UK led to an abortion in 2022 – and single parenthood, as men declined to take responsibility for children that, in their view, women could have prevented. Separating sex even more from marriage and family also meant that men no longer had to be at least potentially responsible providers to get sex.

This pill-driven shift in norms helped to tilt society further in the direction of the hook-up culture and away from the harder-won happiness of committed relationships, towards Milan Kundera’s lightness: living, like one of his unfaithful characters, for fleeting moments of passion and beauty.

When 1970s progressives were battling for women’s equality in the workplace and the home, this is not what they had in mind. Those progressives might be happier when surveying the feminisation of the public realm, though some would note with dismay that the traditional areas of female concern in the family, childcare and care work more generally remain of low status and visibility.

This is an excerpt from The Care Dilemma: Freedom, Family Fertility, now out in paperback and on Kindle. David Goodhart is Head of Demography at the think tank Policy Exchange.