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The latest review of A Billion Years of Sex Differences is out!

It’s by Hannah Barnes in The New Statesman, and I’m happy to report that it’s very positive. I’m particularly excited about this one because The New Statesman leans progressive, so I was bracing myself for a bumpy ride. I’m therefore over the moon that it went down so well. (Admittedly, part of my excitement might be the extra-shot latte I just downed.)

Barnes’s piece is titled “Ignoring sex differences harms us all: The tendency to ignore sex variations harms men and women both – and damages scientific credibility.” Here’s an excerpt:

Men and women are different. But saying so has become taboo, according to the evolutionary psychologist Steve Stewart-Williams. A vocal minority, he states, sees positing the existence of sex differences as “a moral transgression”, to which the typical response is to “cancel, punish and shun”. This is particularly pronounced in academia, where biases distort discussion, he argues. In the Western world, there’s a predisposition towards minimising sex differences. There are other biases. “Studies finding anti-female bias are shouted from the rooftops,” while “those finding no bias or bias against men are reported in a whisper or simply ignored”, Stewart-Williams writes in his new book, A Billion Years of Sex Differences.

This lack of honesty matters. “If we want to make the world a better place, we need good science,” he maintains. That’s not possible “if scientists are afraid to diverge from the pre-specified conclusions of an academic political monoculture”. He argues that not only are there clear differences between the sexes, but the basis for them – in large part – is our “million-year journey of human evolutionary history”. This goes for everything from dating and toy preference to mental and physical health.

“In large part” is key. Stewart-Williams is no gender traditionalist. He rejects those who “exaggerate” differences between men and women. So too, the sex difference-minimisers who argue that if differences exist they’re “a product of discrimination and socialisation” – and that equality requires their abolition. Both views lack balance and fall foul of the science, he says.

Stewart-Williams advocates for a third way: one that acknowledges both nature and nurture, and which neither overstates nor underplays sex differences…

[T]his is an important book. In A Billion Years of Sex Differences, Stewart-Williams is making a more profound argument: magnifying or minimising sex differences doesn’t just ignore science, it leads to harm. By failing to treat us as individuals, we end up discriminating against men and women. In medicine, both exaggerating and denying sex differences can be dangerous: doctors overlook gender atypical problems or presentations, for example missing eating disorders in men and heart attacks in women.

Gender-role individualism is Stewart-Williams’s proffered solution. We should “establish a fair and level playing field”, and let people make informed choices. We can work towards eliminating sex differences “created or amplified by unjust bias or barriers”. But we must acknowledge that “the sexes do differ on average, and we can’t just lie about that”, he says. Instead, we should “tell the truth carefully”.

This is the book’s ultimate message. Truth matters. If we deny differences that “everyone can see with their own two eyes”, the public simply won’t trust scientists on “politically charged topics”. Perhaps that ship has already sailed. Trust in “experts” has been in freefall for years. But an environment in which scientists, politicians, academics and others feel able to tell the truth – however uncomfortable – and not to be punished for doing so, is worth fighting for.

You can read Hannah Barnes’s full review here.

And if you’d like to pick up a copy of A Billion Years of Sex Differences, you can order it here.

Follow me on Twitter/X for more psychology, evolution, and science.

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Steve

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Another highlight of my recent book tour was my trip to the HowTheLightGetsIn Festival in Hay-on-Wye. It was a wonderful festival with a great vibe, amazing food, and stimulating conversations. The organizers really know how to look after their speakers, covering transport to and from the festival, meals, and accommodation in the Welsh countryside - and even providing drivers to ferry us around. I could get used to that kind of treatment…

While I was there, I led a “Champagne, Cake, and Philosophy” event on my book A Billion Years of Sex Differences, caught my first glimpse of the book in the wild (in the festival bookshop), and took part in a debate on the notion of being “spiritual but not religious.” I spotted various famous faces, including Simon Baron-Cohen, Kathleen Stock, and Rowan Williams, and at one point found myself sitting next to Jeremy Corbyn in the green room. And I finally met several people in person who I’d previously known only online, including , , , and .

Meeting Michael, in particular, was long overdue. He wrote the foreword to my second book, The Ape That Understood the Universe, and kindly endorsed A Billion Years of Sex Differences. He also published one of my “12 Things Everyone Should Know” posts in his Skeptic magazine. Despite knowing each other for years, however, we’d never actually met. It turns out we have a lot in common - including remarkably similar stories about how we proposed to our wives.

As well as speaking at the festival, Michael was recording episodes of his podcast, The Michael Shermer Show. He and his Strategy Director, Alexander Reiman, rented a nearby village hall to use as a makeshift studio, and interviewed various festival attendees - including yours truly. Michael and I had a wide-ranging conversation about A Billion Years and various other topics I’ve written about over the years.

Among other things, we discussed:

• The evolutionary origins of sex differences

• Sex-role-reversed species - that is, species where all the usual sex differences are flipped into reverse

• Greater male variability and the Larry Summers controversy

• Why both sexes prefer research that puts women in a better light than men

• Sex differences in STEM

• Whether murder-suicide has an evolutionary basis

• The young male syndrome and sex differences in crime

• Whether IQ is a valid scientific concept or pseudoscientific nonsense

• The replication crisis in psychology

The episode is available on Apple Podcasts, on Spotify, and wherever else you get your podcasts. It’s also available on the Skeptic YouTube channel.

Hope you enjoy it!

• You can order A Billion Years of Sex Differences here.

• You can read the first chapter of The Ape That Understood the Universe for free here.

Follow me on Twitter/X for more psychology, evolution, and science.

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The capacity for violence is one of the oldest and most troubling features of human nature. Why, though, are some people so much more prone to it than others? And why, across cultures and throughout history, have men committed the overwhelming majority of violent acts?

In this extended excerpt from my book, A Billion Years of Sex Differences, I look at what decades of research reveal about one of the largest and most consequential sex differences known to science. Among other things, we’ll see that:

• Men are not only the main perpetrators of violence but also the main victims

• Five lines of evidence point to an innate contribution to sex differences in aggression

• Contrary to popular opinion, the most violent members of society aren’t young men

• Greater male aggression often appears despite culture, not because of it

• Greater male aggression has the same evolutionary underpinnings as the stag’s antlers and male gorilla’s canines

If you enjoy this excerpt, you can explore the full collection of excerpts here, or pick up a copy of A Billion Years of Sex Differences here.

The Strong, Violent Type

Let’s start our tour of the dark side with the antisocial trait that looms above all others: aggression. As mentioned, men are more aggressive than women, at least when it comes to face-to-face or direct aggression. Men shout more, fight more, and kill more. In experiments, they’re more likely to give people electric shocks, and in the real world, they’re less likely to back down from a trivial altercation. Even men tamed by modern civilization – men who’d never throw a punch in real life – watch more violent movies, play more violent video games, and have more fantasies about killing people.

To be fair, when it comes to indirect aggression – spreading rumours about people, excluding them from the group – we find either no sex difference or that women engage in slightly more. For everything else, though, men are in pole position.

As with most sex differences, the sex difference in aggression gets progressively larger for rarer, more extreme acts: a good example of the tail-of-the-distribution effect. Men are somewhat more likely to engage in verbal aggression; much more likely to engage in physical aggression; much, much more likely to engage in violent crime; and much, much, much more likely to kill someone – or, for that matter, to kill themselves.

It’s not that men are vastly more anger-prone than women; the sexes don’t particularly differ in how angry they get or how often. Instead, men tend to be less self-controlled, and less concerned about the negative consequences of overt aggression, from ruptured friendships to injuries and imprisonment.

Few would deny that men are the main perpetrators of violence. Who are its main victims? Many assume that it’s women – and when it comes to sexual violence, they’re right. For every other kind of violence, however, men are more often found in the victim column. This pattern is particularly stark when we look at homicide data. In almost every society on Earth, men are more likely than women to be murdered. Most of the time, the killer is a man as well. Women kill much less often, but when they do, the victim is usually a husband or a boyfriend. Apparently, both sexes prefer to kill men.

Now for the usual disclaimer: The fact that, on average, men are more aggressive than women doesn’t mean that men are the aggressive sex whereas women are the gentle sex. That would be like saying that, because more men than women have a same-sex sexual orientation, men are the gay sex whereas women are the straight sex. Some members of both sexes are highly aggressive, and most members of both are not, at least in the modern world. You know what I’m going to say next, though: Among the minority who are highly aggressive, more are XY than XX.

An Unfortunate Inheritance

Where does the aggression sex difference come from? For some the answer is obvious: culture. A standard cultural explanation would be that, in various ways, society encourages male aggression but discourages aggression in females. Parents, teachers, and peers reward boys for aggressive behaviour, at least in its milder forms. And even when they don’t reward it, they often turn a blind eye to it in boys in a way they never would with girls: Boys will be boys, after all. Meanwhile, movies and other media constantly model male aggression for impressionable young male minds. The subtext is clear: ‘This is the way you should be.’

As always, no one should deny that social factors help shape the sex difference in aggression. But is the difference entirely due to social factors?

Some would say yes. Writing in The New York Times, for instance, psychologist Michael Reichert argued that, although males are more violent than females, this tendency is not innate. However, at least five lines of evidence suggest that Reichert was wrong, and that there’s also an innate contribution.

1. Stubbornness of the Sex Difference in Aggression

One line of evidence for an innate contribution is the fact that the aggression sex difference persists even in the face of countervailing social pressure. Contrary to the idea that we encourage male aggression, parents and teachers spend a lot more time telling boys not to be aggressive than they do girls. This isn’t because they approve more of girls’ aggression; it’s because boys are more often aggressive. But notice the implication: Rather than being created by socialization, the sex difference survives even in the face of socialization in the other direction.

To pre-empt a common misunderstanding, this isn’t to say that socialization has no effect on the sex difference. Clearly, it does; the size of the difference varies considerably from culture to culture and time to time. The point is that socialization couldn’t be the entire explanation, because the difference persists even when socialization pushes harder against male than female aggression. Indeed, socialization may often make the difference smaller than it would otherwise be, not larger.

2. The Developmental Trajectory of Male Aggression

A second line of evidence concerns the unfolding of the aggression sex difference over the lifespan. As psychologist John Archer observed, if socialization alone were pulling the strings, we’d expect to find no difference in aggression in infants, followed by a steady increase in the size of the difference across childhood, as socialization makes its mark on our minds. But that’s not what we find at all.

First, the sex difference in aggression is apparent from the moment kids are mobile enough to make aggression an option: Boys fight more and lash out more, and engage in more rough-and-tumble play. Importantly, these differences appear long before boys and girls start selectively imitating same-sex role models, and long before they even understand that they’re boys or girls.

Second, rather than starting at zero then escalating in boys as the effects of socialization compound, aggression starts out high for both sexes. The most violent category of human being is the toddler, and the only reason we don’t worry more about the epidemic of toddler violence is that toddlers are small and cute, and can’t do much damage with their tiny fists. From this early summit of violence, both sexes become progressively less violent as the years go by. This is a major stumbling block for the theory that children are socialized to be aggressive. To my eye, it suggests instead that they’re socialized not to be. Throughout the process, however, boys are always more aggressive. Is this because anti-aggression socialization is stronger for girls than for boys? No; as we’ve already seen, it’s usually the opposite. But even if it were stronger for girls, the data don’t readily fit with a socialization explanation. Rather than the sex difference getting bigger as children absorb the message that female aggression is less acceptable, the gap remains roughly static throughout childhood.

So far so bad for the socialization hypothesis – and it’s only downhill from here. The next point where the facts come unstuck from the theory is in the decade or so following the onset of puberty. During this biologically critical window, the aggression sex difference suddenly explodes as men ramp up their aggressive antics. The evolutionary psychologists Margo Wilson and Martin Daly dubbed this rapid-onset increase in male misbehaviour the young-male syndrome. The most reliable evidence for the syndrome comes from homicide records. In childhood, neither sex is particularly homicidal. In the years after puberty, however, homicide rates suddenly skyrocket for males. Is this because society starts socializing males to be more aggressive? On the contrary, young male aggression is a serious problem facing every society, and thus most try to restrain rather than inflame it. Nevertheless, it persists.

Finally, as young adulthood gives way to middle age, the sex difference in aggression shrinks, largely because men begin mellowing. The socialization explanation gives us no reason to expect this. As we’ll see soon, though, an evolutionary explanation does.

3. Getting Hormonal

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One of the highlights of my recent book tour was my trip to Austin, Texas, for my second appearance on the Modern Wisdom podcast with .

After flying in from London, I did a one-on-one interview with Chris about my new book, A Billion Years of Sex Differences, followed by a roundtable with Chris, , and Macken Murphy: four hours of podcasting on four hours’ sleep. After that, I took my first ride in a self-driving car. All in all, it was an amazing trip.

Chris and his team released the one-on-one interview last week, and in typical Modern Wisdom fashion, it’s doing the kind of numbers that most podcasters can only dream of. Here’s the blurb for the episode:

Why is it so difficult to talk about the differences between men and women today? It’s important to recognize that men and women deserve equal respect and opportunity, but that does not mean they are exactly the same. There are differences between the sexes that can be meaningful, valuable, and even beautiful. So what are those differences, and why has discussing them become so polarising?

Expect to learn why talking about sex differences is so controversial, what the actual definition of sex is, why there are challenges to the binary idea of sex, the largest sex differences between men and women, how sex differences reveal themselves via personality, the danger of denying and/or not respecting the differences in sex, and much more…

The episode is available on Apple Podcasts, on Spotify, and wherever else you get your podcasts. It’s also available on Chris’s YouTube channel.

If you enjoy the conversation and would like to explore these ideas in greater depth, you can pick up a copy of A Billion Years of Sex Differences here.

Buy A Billion Years

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Steve Stewart-Williams

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A fascinating new paper explores the evolutionary psychology of parental care, and comes to two major conclusions.

First, parents differ in how they treat their sons vs. their daughters: Daughters receive more relationship guidance, protection, and emotional support, whereas sons receive more athletic training and encouragement to be competitive. Sons also have fewer restrictions on their sexual behavior.

Second, mothers and fathers differ in the types of parental care they provide. Mothers are more involved in direct care, bonding, social/moral guidance, and discipline. Fathers are more involved in athletics and in teaching mechanical and practical skills.

These findings are summarized in the following graph.

According to study authors Francis (Sid) Dougan, William Costello, and David Buss, these results make good evolutionary sense. Throughout our evolutionary history, daughters and sons faced different adaptive problems, and needed different kinds of parental input. At the same time, evolved differences between men and women meant that fathers were often better equipped to provide certain forms of input, while mothers were better equipped to provide others.

Here’s the abstract of the paper:

Most research on human parental investment has focused on overall parental effort or resource allocation, overlooking the fact that human investment spans a broad suite of material, instructional, and social forms of investment. This array of investment enables examination of how evolutionary processes have elaborated parental care into distinct domains. Where daughters and sons historically faced different recurrent adaptive problems, selection should have favoured biases in parental investment that cultivate in each offspring the competencies relevant to its sex-specific challenges (e.g., navigating greater reproductive costs for daughters; navigating contest competition for sons). Likewise, mothers and fathers should differ in parental investment domains where their own evolutionary and life histories afforded greater sex-specific expertise. To test these hypotheses, we used linear mixed-effect models to analyse 105 adults’ (49.5% female) ratings of parental investment received across 73 behaviours organised into 13 domains. Results were largely consistent with predictions. Daughters received more parental investment in mating and relationship guidance, protection, and material support. Sons received greater parental investment in athletic training, permissiveness regarding sexual behaviour, and competitive encouragement. Mothers invested more than fathers in direct care, bonding, social and moral guidance, and discipline. Fathers invested more in athletics, and mechanical and practical skills. Domains linked to adaptive challenges common to both sexes (e.g., direct care) showed no offspring-sex differences in parental investment. The patterns accord with the evolutionary hypothesis that parental investment maps onto sex-differentiated adaptive problems. Discussion explores hypotheses about the interactions between socialisation practices of parents and sex-linked predispositions in offspring.

• You can access the paper for free here.

• You can read a user-friendly Twitter/X thread about the research by first author Sid Dougan here.

• I discuss the evolution of sex differences in parental care in my new book, A Billion Years of Sex Differences, and in my earlier book, The Ape That Understood the Universe.

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1. Like and Restack: Click the buttons at the top or bottom of the page to boost the post’s visibility on Substack.

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This is the latest post in my “12 Things Everyone Should Know” series. You can access the full collection here.

To mark the publication of my third book, A Billion Years of Sex Differences, I’m releasing a post I’ve had in mind for several years, but that I thought I should save until the book was out: 12 Things Everyone Should Know About Sex Differences.

Few topics in psychology generate more heat than this one, but few are backed by a larger body of scientific evidence. The aim of this post is to highlight some of the best-established differences in the scientific literature, and what the research says about their origins. Are they due solely to culture, or is there also an innate component? If the latter, why did the innate component evolve?

Before getting started, though, a warning: It’s easy to misunderstand claims about sex differences. The image below explains what scientists mean - and what they don’t mean - when they say that, on average, men score higher than women on a given trait (or vice versa).

With that in mind, let’s start our exploration of some of the key findings from the science of sex differences.

1. On average, men are more interested than women in casual sex and sexual variety. Note that this isn’t to say that “Men are promiscuous, women monogamous”; it’s an average difference, not a categorical one. The table below summarizes some of the voluminous evidence that the sexes differ in this domain.

2. On average, men place more weight than women on a long-term mate’s looks - see the first graph below. Women, in contrast, place more weight than men on a mate’s wealth and status - see the second graph below. Both differences are found in all or almost all nations; the graphs just show a representative sample.

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I recently appeared on one of the best-named podcasts in Podcastistan: the Maiden Mother Matriarch podcast with . We discussed various topics related to my new book, A Billion Years of Sex Differences, including:

• The largest psychological sex difference in our species. Can you guess what it is?

• The tail-of-the-distribution effect: the fact that even small sex differences at the mean translate into large differences at the extremes of the distribution

• When sex stereotypes are right and when they’re wrong

• Sex differences in direct vs. indirect aggression

• Whether women perpetrate as much intimate partner violence as men

• Sex differences in occupational choice

• The downsides of affirmative action for women

• The greater male variability hypothesis and why it’s controversial

• The gender-equality paradox: Is it real?

• Why we’re still in denial about sex differences

The episode is available on Apple Podcasts, on Spotify, and wherever else you get your podcasts. It’s also available on Louise’s Maiden Mother Matriarch Substack.

You can pick up a copy of my book, A Billion Years of Sex Differences, here.

Buy A Billion Years

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This post is free to read for all, so please feel free to share it.

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For as long as I can remember, the standard story in the social sciences has been that women and minorities are routinely discriminated against in STEM fields: Their research is judged more harshly, and they’re less likely to be hired or promoted. Evidence is mounting, however, that this story is increasingly out of date. A new preprint reports that, when evaluating identical CVs, STEM professors in the United States rate the research records of women and Black people as superior to those of men and White people, and are more likely to recommend them for promotion or tenure.

The key results of the research are shown in the following table.

This pattern is plausibly the result of efforts to correct for historical anti-female and anti-Black bias. Rather than eliminating that bias, however, we seem to have inadvertently reversed it, at least in some domains.

The research was conducted by Deborah Wu and Nilanjana Dasgupta. Here’s the abstract of their paper:

Gender and race disparities persist among tenure-track faculty in the United States, especially in STEM, where women hold 26% of academic positions and Black and Hispanic faculty together comprise only 7%. We conducted a randomized controlled experiment with 796 tenured biology and chemistry professors employed at 183 U.S. doctoral-granting institutions to investigate their evaluation of pre-tenure faculty’s research readiness for tenure and promotion in research-intensive universities. Faculty received an identical CV with only the candidate’s name varying to signal their gender and race, using a 2 Race (Black vs. White) by 2 Gender (male, female) between-subjects factorial design. Results revealed that STEM faculty evaluated female and Black candidates’ research record significantly more favorably and recommended them for tenure and promotion at higher rates, compared to male and White candidates with identical CVs. Findings remained largely consistent even after controlling for faculty participants’ own gender, race, and rank. We speculate that social norms about diversity, equity, and inclusion prominent in 2020-21 when these data were collected during the COVID-19 pandemic and shortly after George Floyd’s murder may have heightened faculty’s awareness of gender and race bias, increased motivation to be fair in decision-making, and led to compensatory judgments to increase diversity in STEM careers.

Note that, in the Discussion section of the paper, Wu and Dasgupta offer the following caution:

Our studies were conducted during a time in which promoting faculty diversity was widely accepted and encouraged. The current climate in higher education has drastically shifted away from discussing diversity in employment since the federal executive orders of 2025 under the Trump administration, which may alter how academic leaders approach these decisions today. The observed favoring of Black and female candidates over others may not generalize to our current-day context and to other environments in which diversity norms are less prescriptive.

My guess is that the bias would still be found; the government rules have changed, but STEM professors’ attitudes and values probably haven’t. Still, this is an empirical question, and it will be interesting to see how future research pans out.

• You can access Wu and Dasgupta’s paper here for free.

• I discuss bias in favor of women in STEM in Chapter 10 of my book, A Billion Years of Sex Differences.

• HT for pointing me to this paper.

Follow me on Twitter/X for more psychology, evolution, and science.

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Many of our most strongly held beliefs about gender, race, and inequality turn out to be mistaken.

In this third installment of my series on popular social-science myths (see also here and here), I look at six more claims that are widely accepted but poorly supported by the evidence. Among other things, we’ll see that voters may be less sexist than people assume, that women’s health is not as neglected as we’re often told, and that some of our most cherished assumptions about war, poverty, and economic inequality don’t stand up to scrutiny.

As always, my aim isn’t to push a political agenda but simply to compare popular narratives with the available data. The results, I think, are both surprising and illuminating.

1. The Myth of Voter Sexism

Americans tend to overestimate voters’ prejudices against women and ethnic minorities. Democrats are particularly prone to this - which ironically makes them less likely to support female or minority candidates due to concerns about electability.

2. The Myth That Women’s Health is Ignored

We’re often told that men’s health gets more funding and attention than women’s. Various datasets suggest, however, that it’s actually the other way round. The graph below, for instance, shows relative investment in women’s vs. men’s health in Australia over the last decade or so. Throughout that time, women’s health received considerably more funding than men’s.

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This is the latest excerpt from my book, A Billion Years of Sex Differences. You can access the full collection here, or pick up a copy of the book here.

In this installment, we’ll see…

• How mate choice shaped the evolution of men’s and women’s minds

• Why women care more about their looks and men about their status and wealth

• How sexual selection explains women’s greater proneness to body-image problems

• The evolutionary roots of eating disorders and “bigorexia”

• Why evolved mate preferences help explain the gender pay gap

Why Mate Choice Matters

Let’s now tiptoe into more controversial territory. Mate preferences not only help shape men’s and women’s bodies, they also help shape their minds. If people want a smart mate, a kind mate, or a funny mate, the species will inevitably evolve to be smarter, kinder, and funnier. Not only that, but we’ll evolve a motivation to hone and display the traits that potential mates desire.

You can probably see where I’m going with this. Because the sexes have somewhat different desires, each may have evolved somewhat different traits – and also somewhat different priorities about which traits to hone and display. How might this have played out in our species?

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Many people think of prejudice as primarily a right-wing phenomenon. Philosopher Mike Huemer argues instead that it’s found right across the political spectrum. In his view, many contemporary progressives display the same psychological tendencies associated with older forms of bigotry, just directed at different targets.

Below is a brief excerpt from an excellent Substack essay he recently published on the topic, titled “Progressive Intellectuals: Image vs. Reality.” If you enjoy it, be sure to check out the full essay - it’s well worth your time.

If you move in even moderately high-status circles in our society, you’re basically never going to run into right-wing bigots. But you’re going to be repeatedly bombarded by left-wing bigotry...

Some manifestations of this prejudice:

1. Collectivist obsession

Progressive intellectuals are obsessed with race, sex, and other “identity groups”, far more so than normal Americans... When two people have a conflict, the progressive “anti-racist” needs to know the races of the two people before he decides which side he is on. The “anti-sexist” feminist needs to know the genders of the two people.

2. Animosity

A classic feature of racism is animosity toward one or more particular races. In traditional, right-wing racism, that would be hatred toward blacks, Jews, Latinos, and perhaps Asians. Traditional sexism involves having lower respect for women (though perhaps not hatred).

In contemporary, left-wing racism, we see hatred toward white people, and perhaps Jews, and perhaps Asians. (The Jews get it from both sides.) In left-wing sexism, we see hatred and contempt for men.

Progressives don’t like to think of themselves as hate-mongers. But if someone talked about any other group the way progressives talk about white men—e.g., talking about the harms of “whiteness”; going on about wrongs committed by white men, emphasizing their race and sex, while passing over wrongs committed by other groups—progressives would take one nanosecond to label that “hate speech”.

3. Scapegoating

Progressives like to blame white people for most of the world’s problems. This is another classic feature of racism. Right-wing racists such as the Nazis tried to blame the Jews for most of society’s problems. It doesn’t cease to be racism just because you pick a different race to scapegoat.

4. Stereotyping

Another classic feature of racism: negative stereotyping. Traditional racists would stereotype Jews as greedy, blacks as criminals, etc. Traditional sexists stereotype women as less capable than men. Left-wing bigots, on the other hand, stereotype white men as abusers and oppressors, and other groups as victims of white males.

That is the first element of progressive self-deception: they style themselves warriors against prejudice, but they are the biggest force stoking prejudice in our society. They think that their prejudice is different because the group they’re attacking is actually bad. They don’t see their stereotypes as stereotypes but just as the truth. That, of course, is what all bigots think.

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Welcome to the June 2026 edition of the N³ Newsletter Linkfest: a collection of links to papers and articles that grabbed my attention over the last month. On the menu today…

• Why you should be wary of people who want to be seen as highly moral

• How GLP-1s affect dating and employment

• Casual sex and self-esteem in men vs. women

• Homosexuality in rats

• The surprising connections between mental and physical health

Around half the items are free to read for everyone; the rest are for paid subscribers only. I tend to put my spicier content behind a paywall, so if you’ve got a high spice tolerance, consider becoming a paid subscriber.

You can access the complete collection of Linkfests here.

Special Summer Deal

To celebrate the publication of my book A Billion Years of Sex Differences, I’m offering 20% off subscriptions to The Nature-Nurture-Nietzsche Newsletter for the next week. Redeem your special offer today!

Redeem Special Offer

How Many Senses Do We Have?

Most people would say five - but according to many neuroscientists, we have a lot more than that. Depending on how we slice the cake, we might have ten, or maybe 21, or maybe 33. [Link.]

GLP-1s and the Female Obesity Penalty

A new study suggests that weight loss can have effects far beyond health. Among women starting GLP-1s, single women were more likely to enter relationships, and unemployed women were more likely to find work. Women already in relationships or employment saw little change, suggesting that the “obesity penalty” operates largely through first impressions during the early stages of relationship formation or hiring. [Preprint; Link.]

Evolutionary Mismatch in the Classroom: Boys Are More Mismatched Than Girls

Why do more boys than girls struggle in the classroom? Part of it may be mismatch between the demands of school and boys’ evolved nature. To start with, boys are, on average, more physically active than girls and less suited to prolonged sitting and verbal instruction. As a result, they’re more likely than girls to be flagged as having behavioral difficulties. On top of that, schools often fail to capitalize on boys’ relative cognitive strengths in spatial and mechanical reasoning. [Link.]

Are Free Speech Advocates Secret Racists?

Nope. Across multiple datasets from multiple nations, people who placed more value on free speech were more likely to hold racially tolerant attitudes. This is consistent with the idea that free speech and tolerance spring from the same broader liberal ethos. [Link.]

The Ideological Turing Test

Can you describe your political opponents’ views so well that they wouldn’t be able to tell whether you agree with them? If so, you’ve passed the “ideological Turing test,” an informal measure of how well you understand your opponents’ positions. According to new research, people who do better on this test - that is, people who understand their opponents’ views better - tend to be less hostile toward their opponents: They see them as less ignorant, less irrational, and less immoral. [Link.]

Do Men Earn More? If So, Which Ones?

Everyone’s heard the claim: Men earn more than women. According to recent data, however, the generalization isn’t quite right. A more accurate formulation would be that married men earn more than women, and also than single men. Single men, in contrast, earn no more than women. Is this because men knuckle down when they marry, or because women are more likely to marry high earning men? It seems to be largely the latter. [Link.]

Women in Academia Do Just as Well - Until They Become Mothers

Before they have children, women do roughly as well as men in academia. Afterwards, however, women fall behind. What explains this pattern? Candidate explanations include that academia discriminates against mothers rather than women in general (seems unlikely); that despite considerable efforts to improve things, the demands of an academic career are still hard to juggle with motherhood (could be part of it); and that women’s priorities change after having children (seems like a plausible contributor). [Link.]

Moral Double Standards

People who want the world to see them as highly moral are more likely to judge others harshly, while turning a blind eye to their own moral failings. [Link.]

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You can now watch my recent appearance on the Art of It podcast with Neo McNulty. We had a fun, wide-ranging conversation about evolutionary psychology and my new book, A Billion Years of Sex Differences. Here are some of the many topics we covered:

• What is evolutionary psychology?

• The evolution of sex differences in humans and other animals

• Human sex differences, ranked from largest to smallest

• Why sex differences in our species are smaller than those in most other mammals

• The evolution of romantic love

• The manosphere

• The Cinderella effect

• Why “natural” doesn’t mean “good”

The episode is available on Spotify, on Apple Podcasts, and wherever else you get your podcasts. You can also watch it on Neo’s Art of It YouTube channel.

Buy A Billion Years!

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How You Can Support the Newsletter

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Thanks!

Steve

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In Case You Missed It…

• Should We Trust Social Science Research?

• 10 Highly Replicable Findings from Psychology

• Top 10 Most Replicable Findings from Behavior Genetics

Introductory psychology textbooks still haven’t caught up with the science. Despite years of criticism, they continue to promote debunked research, to present psychology as more settled than it is, and to be overly credulous of ideas that buttress progressive political pieties.

Among other things, many intro psych textbooks gloss over flaws in famous studies such as the Stanford Prison Experiment; misrepresent areas like evolutionary psychology; present highly contested but left-friendly ideas like stereotype threat as settled science; promote psychological myths such as that violent video games cause real-world violence; and ignore exaggerations and distortions in famous case studies like that of Phineas Gage and Kitty Genovese.

The relative frequencies of these and other errors are shown in the table below.

The table comes from a recent paper by Jeffrey Brown and Christopher Ferguson. Here’s the abstract:

Recent scholarship has identified that factual errors have been common in introductory psychology textbooks. These errors tend to be in the direction of making psychological research appear more consistent than it is, as well as promoting viewpoints consistent with politically progressive ideologies. Some famous experiments in psychology have also seen serious questions raised about their validity. Given that these conversations have gone on for about a decade, it is worth considering whether identification of these issues resulted in improved coverage in introductory textbooks. Textbooks were sampled at two time points. Sixteen textbooks were sampled in 2018, and 18 in 2023. Although some improvements are seen from earlier studies, results indicated that errors in textbooks have remained common even after this issue had been clearly identified in the published literature. Misreporting of basic scientific information remains common in introductory textbooks, despite improvements in some areas. Textbook authors should be alert to potential misinformation, particularly related to controversial topics. Introductory psychology teachers may need to be aware that not all information presented in textbooks is true.

You can access the Brown and Ferguson paper here, or request a free copy from the authors here.

Follow me on Twitter/X for more psychology, evolution, and science.

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How You Can Support the Newsletter

This post was free to read for all. If you like what I’m doing with The Nature-Nurture-Nietzsche Newsletter, and want to support my work, there are several ways you can do it.

1. Like and Restack: Click the buttons at the top or bottom of the page to boost the post’s visibility on Substack.

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If you could do any of the above, I’d be hugely grateful. The support of readers like you helps keep this newsletter going.

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Steve Stewart-Williams

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In Case You Missed It…

• 12 Things Everyone Should Know About Evolutionary Psychology

• 12 Things Everyone Should Know About Behavior Genetics

• The Second Law of Behavior Genetics

I recently sat down with Nikil Mukerji and Timur Sevincer of the German skeptic group GWUP to discuss evolutionary psychology, nature and nurture, and my new book, A Billion Years of Sex Differences. The interview appeared in Skeptiker magazine last week, but Nikil and Timur kindly agreed to let me reproduce it here.

Before we get to that, though, a quick request. This article is free to read for everyone. If you enjoy it and would like access to all Nature-Nurture-Nietzsche content, please consider becoming a paid subscriber.

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Paid subscriptions also help support my efforts to explore important and controversial topics, and give me the financial freedom to follow the evidence wherever it leads without fear of cancellation.

Thank you - and now, on with the interview.

In this conversation with Timur Sevincer and Nikil Mukerji, Steve Stewart-Williams discusses what evolutionary psychology actually claims, how the field can deepen our understanding of human nature, where the field has gone wrong, why the charge of pseudoscience misses the target, and how skeptics should respond when real science becomes politically unwelcome.

Common Misunderstandings About Evolutionary Psychology

Timur Sevincer: As skeptics, we care about pseudoscience, but also about exaggerated, distorted, or plainly false scientific claims. Which claims about sex differences or evolutionary psychology are most often misrepresented?

Steve Stewart-Williams: The list is long!1 A common view is that evolutionary psychology is a way to justify existing social roles, especially traditional sex roles. Another is that it’s a way to excuse misbehaviour, especially male misbehaviour. I think both claims are false.

Explaining a behaviour is not the same as morally justifying it. To think otherwise is to commit the naturalistic fallacy – the mistaken assumption that what’s natural is therefore morally right. We have to decide for ourselves what’s right and wrong. We shouldn’t let natural selection dictate our ethics. Evolution can explain behaviour without excusing it.

Another common claim is that evolutionary hypotheses are unfalsifiable. I don’t think that’s true either. Evolutionary hypotheses are falsifiable,2 and many have been falsified. More of my own hypotheses than I’d care to admit have been falsified. I’ve come up with a hypothesis and done the research, then the world has said: No, you’re wrong about that.

A further misunderstanding is that evolutionary psychologists think men and women are virtually different species: women are monogamous, men are promiscuous; women are choosy, men will sleep with anything that moves; men care only about a woman’s looks, women only about a man’s resources. None of this is what evolutionary psychologists claim. Most human sex differences are statistical differences with large overlap. Both sexes can form committed relationships and both can be interested in casual sex. Both sexes are choosy about long-term partners and both care about looks.

Finally, many people assume that if a trait has an evolutionary component, it must therefore be fixed or biologically predetermined. But that’s not the claim. Genes may push development in certain directions, but they’re not the only influences. Learning, culture, incentives, and institutions also matter.

Timur Sevincer: I teach open-minded, curious, and intelligent students. However, some of these misunderstandings seem to be very common before they engage with evolutionary psychology in more depth. In rare cases, some course evaluation comments continue to portray evolutionary psychology as pseudoscience even after extensive discussion of overwhelming empirical evidence. Those ideas must come from somewhere.

Steve Stewart-Williams: Yes. I’ve encountered that too, though less in Malaysia, where I now teach, than in the UK. Some people appear to associate evolutionary psychology with outdated or harmful ideas before they’ve really looked at the evidence. They’ve picked up widespread but mistaken views about the field. I think there’s been a successful misinformation campaign against it.

For many people, though, it’s possible to persuade them that, even if some evolutionary psychological ideas turn out to be wrong, the motivation isn’t bad. Evolutionary psychologists aren’t trying to drag the world backwards.

Is Evolutionary Psychology Pseudoscience?

Nikil Mukerji: Do you have a specific concept of pseudoscience in mind? I ask because this is one of my own areas of work.

Steve Stewart-Williams: In that case, I’ll say no and ask you for your definition!

Nikil Mukerji: Pseudoscience is not simply unfalsifiability. Some pseudosciences, such as homeopathy, are eminently falsifiable and have been falsified. The core issue is that they fake doing science.

Frankfurt describes bullshit as indifference to truth.3 I think one can extend this idea. Every practice has constitutive norms. Science is governed by truth-directed norms: heeding evidence, testing claims, trying to find out what is the case. Pseudoscience fakes participation in that truth-seeking practice.

Steve Stewart-Williams: That rings true to me.

Nikil Mukerji: That is why the pseudoscience charge cannot be a mere insult. One has to say what exactly is wrong with the claim or field. Does it avoid falsification? Does it ignore counterevidence? Does it only imitate the surface of science?

Steve Stewart-Williams: Exactly. Anyone can say, “You’re a pseudoscientist!” It’s like that Spider-Man meme where the two Spider-Men point accusingly at each other. The label alone doesn’t settle anything. You have to say what, specifically, is wrong with each claim.

Claims in evolutionary psychology aren’t all equally strong. Some are weak, some have been falsified – but some are excellent. The right approach is to avoid thinking “evolutionary psychology is all good” or “evolutionary psychology is all bad,” and instead to evaluate each assertion on its merits.

A Field That Can Be Wrong

Timur Sevincer: You said evolutionary hypotheses can be falsified. Could you give examples?

Steve Stewart-Williams: A famous example is the kin-selection explanation of same-sex sexual orientation, associated with E. O. Wilson. Same-sex sexual orientation is puzzling in evolutionary terms. Wilson suggested that it might be a form of kin altruism: instead of having children of one’s own, someone might help siblings or other relatives to have children, thereby passing on their genes indirectly through them.4 But people did the research, and the verdict seems to be that this isn’t the explanation.5

Timur Sevincer: Another example might be the dual-mating or ovulatory-shift idea: the idea that women might seek investment from one kind of man and “good genes” from another, with preferences shifting around ovulation. There were T-shirt smell studies and other work that initially attracted considerable attention,67 though the literature has since become more contested. How would you evaluate the state of the evidence today?

Steve Stewart-Williams: I’m very skeptical of the ovulatory-shift hypothesis. To be fair, the debate isn’t over; there are still people on both sides of the issue. But I’m much more persuaded by the people who say that the evidence hasn’t borne it out.

Timur Sevincer: How does evolutionary psychology fare after the replication crisis?

Steve Stewart-Williams: It hasn’t emerged unscathed, but I think it fares fairly well. It does better than social psychology, though not as well as behaviour genetics. The most robust claims in the field are those grounded in well-established theories from evolutionary biology: sexual selection theory, parental investment theory, parent-offspring conflict theory, kin selection theory. These aren’t just free-floating speculations. They’re grounded in principles that have been demonstrated across many species. This is especially true for many sex differences.

Another reason the field has done well in certain areas is that it was seen as controversial from the outset. To persuade people, evolutionary psychologists have often had to clear a higher evidential bar. David Buss’s work on mate preferences, which found that men and women differ on average in how strongly they prioritize certain traits in long-term partners, used extensive cross-cultural evidence.89 Martin Daly and Margo Wilson’s work on homicide and step-parenthood, the so-called “Cinderella effect,” that children are at greater risk of abuse and violence from stepparents than from biological parents, drew on large archival datasets.10 The sex difference in interest in casual sex has multiple converging lines of evidence: cross-cultural evidence, real-world dating data, cross-species patterns, and links to prenatal hormonal exposure.11

Nikil Mukerji: There is an interesting complication here. A low replication rate can be a warning sign. But in some pseudoscientific or ideological literatures, one finds suspiciously high positive-result rates: everything seems to confirm the preferred story. So a perfect replication rate can be suspicious as well.

Steve Stewart-Williams: Yes. To do replication properly, you need open science practices, preregistration, methods that could falsify the hypothesis, and ideally multiple research groups, including people with different prior commitments. Even if a claim is falsifiable in principle, one isn’t really doing science unless one uses methods that could in principle falsify it.

Social psychology deserves credit here. The fact that we know about its replication problems shows that many in the field are testing their claims and trying to improve. A low replication rate isn’t fatal if researchers are actively checking their findings and weeding out false positives. The problem is that, until recently, they often weren’t.

The Ethical Trap

Nikil Mukerji: Some findings in evolutionary psychology are bound to annoy people, especially in certain political milieus. Are you concerned that this kind of science might play into the wrong hands? How do you deal with the ethics of communicating sex differences?

Steve Stewart-Williams: That’s a good and difficult question. Claims about sex differences can certainly be misused. They can be misused if people exaggerate the size of the differences. They can also be misused if people infer that, because a difference has an evolutionary basis, it’s therefore good or should be preserved. That can do harm. If we exaggerate differences, we may lower our expectations for one sex in certain domains.

But I have two responses. First, the sexes do differ on average, and I think there’s an evolutionary contribution to some of those differences. We can’t just lie about that. The right response is to tell the truth carefully and responsibly.

That means emphasising that most human sex differences aren’t huge.1213 There’s a lot of overlap between the sexes. Everyone should get a fair chance. And the fact that something is natural, genetic, or partly shaped by evolution has no direct moral implications. Natural selection doesn’t tell us what’s right or wrong.

Second, denial can also do harm. It’s not the case that exaggerating sex differences is dangerous while minimising them is harmless. We can get this wrong in both directions.

Nikil Mukerji: So denial is wrong in principle, and one can also make a consequentialist case against it.

Steve Stewart-Williams: Exactly.

Timur Sevincer: This is also a communication problem. Many people hear “sex differences” and immediately think one is defending misogyny or fixed social roles. In my own teaching, I often begin by saying: there is usually substantial overlap between the sexes, most differences are small, evolutionary influences don’t make differences fixed or unmalleable, and a trait’s evolutionary origins don’t make it morally good.

Nikil Mukerji: And acknowledging average differences doesn’t necessarily make people conform to them. In some cases, it could even have the opposite effect: if people are aware of an average tendency, they may consciously decide not to follow it. Recognising statistical differences and encouraging individuality are not incompatible.

Steve Stewart-Williams: I think that’s right. It’s also important to take people’s concerns seriously. Some people worry that evolved sex differences will be used to revive old claims about male superiority or fixed gender roles. Given our history of anti-female sexism, that worry is understandable. But the right response isn’t to shut down the discussion. The right response is to discuss the evidence carefully.

Socialisation, Stereotypes, Patriarchy

Timur Sevincer: When people think about sex differences, they often default to three explanations: socialisation, stereotypes, and patriarchy. Boys and girls are raised differently; stereotypes become self-fulfilling; women are forced into roles by structures created by men. You deal with these explanations in A Billion Years of Sex Differences. Where do they fall short?

Steve Stewart-Williams: Well, let me start by saying that I think “fall short” is the right phrase. It’s not that they have no merit. It’s impossible to believe that socialisation has no impact on behaviour. Stereotypes have an impact. Cultural factors matter. But they’re not enough on their own.

Take parental treatment. It’s often invoked as an explanation for sex differences. But there’s research suggesting that, at least in the West, parents don’t treat sons and daughters particularly differently in many important ways.14 Behaviour genetics also suggests that, within the normal range, the shared family home doesn’t have a massive impact on how people turn out.15 This doesn’t mean genes explain everything. The environment matters too. But the simple parental-socialisation story is weaker than many people assume.16

On patriarchy, the gender-equality paradox is a serious problem for simple versions of the story. For many traits, sex differences are larger, not smaller, in wealthier, more individualistic, more gender-equal nations.1718 That’s the opposite of what one would expect if the differences were due to strict sex roles or patriarchy. I’m not saying that every difference follows this pattern, or that culture is irrelevant – in fact, the gender-equality paradox is itself a cultural effect. What I am saying, though, is that it challenges certain traditional sociocultural explanations for differences between the sexes.

On stereotypes, the work of has been a major influence on me. Stereotypes can be self-fulfilling to some extent, but the main causal direction is usually from social reality to stereotype, not from stereotype to social reality.19 In the case of sex differences, stereotypes are partly shaped by actual average differences that people perceive in the world, and they correspond reasonably well to the actual sex differences.20 In some cases, those stereotypes might then amplify or galvanize the differences. But they don’t create them out of nothing.

Nikil Mukerji: There is a habit of reasoning that often gets in the way here. Instead of asking whether a claim is true, one asks: “What makes you say that?” and “Who does this help?” Truth recedes into the background.

Steve Stewart-Williams: That can become a form of conspiracy theorising. If someone says, “You only believe that because you’re a man,” or “You only believe that because you’re defending your group,” that’s a claim about motive. But even if the motive attribution were true, it wouldn’t show that the claim is false. It’s essentially just an ad hominem argument.

What Denial Costs

Timur Sevincer: Many people understand that exaggerating sex differences can do harm. What is less obvious to many is that downplaying differences can also do harm. Can you give examples?

Steve Stewart-Williams: Sure. I discuss various examples in the book. One is that, if we minimise sex differences in psychological disorders, we may fail to spot them in the less affected sex. ADHD often presents differently in girls than in boys, and the standard description fits boys better. That means girls with ADHD may be overlooked. Autism may also be overlooked in girls because it presents differently than in boys – for example, it tends to involve fewer repetitive behaviours. Conversely, depression in men more often involves substance use and aggression than in women, so male depression may be missed.

There are social and occupational examples as well. If we ignore average differences in occupational interests, we may assume that every gender gap in a field is due entirely to bias. Bias exists, but sex differences in interests also matter. Men are, on average, more interested in things and things-related jobs; women are, on average, more interested in people and helping professions.21 If we ignore that, we may misdiagnose the cause of gaps and pour resources into interventions that don’t address the real causes.

It can also lead to coercive policies. If one reserves positions for one sex, or chooses a less qualified candidate to achieve numerical parity, one may reverse bias rather than remove it. On top of that, it can cast doubt on the competence of the supposedly benefited group. Even beneficiaries themselves may wonder whether they really deserved the position. And portraying STEM as saturated with sexism may deter some girls and women who would otherwise enjoy those fields.

Discrimination exists. But exaggerating it, and ignoring the progress that has been made, can backfire.22 And we shouldn’t overlook the fact that there’s also evidence of discrimination against men in some hiring contexts.2324

The Slippery Word “Gender”

Nikil Mukerji: In the book, you are quite critical of the concept of gender. Could you explain why?

Steve Stewart-Williams: I don’t think it’s a very useful concept, partly because it’s not just one concept. Sometimes “gender” is just a synonym for sex. Sometimes it refers to masculinity and femininity. Sometimes it refers to sex differences supposedly due to nurture rather than nature. Sometimes it refers to social roles, stereotypes, gender identity, or clusters of personality traits.

The nurture-based definition is especially problematic. It often assumes what should be demonstrated: namely, that nurture is the sole cause of the difference. Many recurring male-female differences involve both nature and nurture. If one defines gender as the nurture part and sex as the nature part, most female-male differences become partly sex differences and partly gender differences. That’s an awkward way to frame things.

Other definitions have other problems. If “gender” means personality profiles, for instance, then the claim that there are many different genders collapses into the trivial observation that every person has a unique personality profile. At that point, we’re talking about personality, not something clearly linked to sex.

For these and other reasons, I prefer to talk about sex rather than gender. In biology, sex is defined by gametes: females are organised around the production of eggs; males around the production of sperm. Sex-linked traits such as chromosomes, genitals, hormones, masculinity, femininity, sex-typical behaviour, and personality traits don’t define sex. Instead, they’re among the many traits that evolved to facilitate reproduction via either eggs or sperm.

Why This Topic Can Set Rooms on Fire

Timur Sevincer: Why do sex differences, sexual behaviour, and evolution sometimes provoke such strong emotions? In principle, one could discuss them scientifically.

Steve Stewart-Williams: The topic is inherently combustible. A big part of the reason is our history of sexism against women. Early scientists made false and sexist claims about women’s intellectual abilities. So it’s understandable that people worry. If we open the door to evolved sex differences, are we going to slide back into Victorian ideas about male superiority and fixed roles?

But the science of sex differences actually refutes those early sexist claims. Shutting down the discussion is the wrong reaction. We should be able to say: Yes, some past claims were wrong and sexist; no, that doesn’t mean every claim about sex differences is wrong or sexist.

Unfortunately, a modern trend on campus and elsewhere is to fight unwelcome ideas not with arguments and evidence, but with accusations, complaints to authorities, protests, occupations of classrooms, and so on. These are intimidation tactics as much as anything else. It’s anti-intellectual. In principle, anyone with any view can use intimidation tactics. Thus, intimidation can’t sort out who’s right and who’s wrong.

I had my own taste of this. A paper I wrote on sex differences in STEM25 caused an online controversy and led to calls for retraction. The issue reached the equality, diversity, and inclusion (EDI) office at the University of Nottingham’s UK campus. They did not like the paper! To their credit, though, they defended my academic freedom, and I was promoted to full professor despite listing the paper as one of my main pieces of work. But the experience was still worrying. I didn’t seriously think I’d lose my job, but I did wonder whether expressing perfectly reasonable views about sex differences might make it difficult for me to get another academic job.

That was part of why I started my Substack, The Nature-Nurture-Nietzsche Newsletter. I wanted a fallback. If the worst came to the worst, I wanted another way to make a living. And it’s worked out well: I’m no longer financially dependent on my academic job. It’s a great position to be in. I’ve always tried to write honestly and openly about the topics I cover, even when knowing it might not be popular. But now I do so with a lot less trepidation.

Can Persuasion Still Work?

Nikil Mukerji: Some of these controversies are not only about evolutionary psychology itself, but also about deeper disagreements concerning evidence, reasoning, and the interpretation of scientific claims. How does one talk to people who have been taught that logic is a tool of oppression? They often fail to separate the truth of a claim from alleged motives for making it.

Steve Stewart-Williams: Even people who officially reject reason and evidence may still be moved by logical arguments. They might not change their minds immediately, but they may eventually. Social psychologists call that a sleeper effect, and it’s a well-documented phenomenon.

Nikil Mukerji: My suspicion is that another causal factor is needed. Some people change their minds after reality punches them in the face. Then they remember that someone had explained the matter differently.

Steve Stewart-Williams: That could well be right. But persuasion is still worth attempting. It won’t work on everyone. Nothing will work on everyone. But across history, humanity has moved away from superstition toward more scientific ways of thinking. That suggests that slow persuasion is possible.

Can Evolutionary Science Inform Moral Reasoning?

Nikil Mukerji: In A Billion Years of Sex Differences, you rightly reject the inference from “natural” to “good.” But Wilson and colleagues26 argue that evolutionary psychologists often overcorrect here: Hume’s point is only that ought cannot be derived exclusively from is, not that evolved facts have no ethical relevance. So when you say that the science of sex differences cannot answer policy questions because those are ultimately about values, how do you avoid turning a valid warning against “natural = good” into a stronger and false separation between facts and ethics? More concretely: should evolved sex differences alter our moral and political reasoning about fairness, coercion, individual freedom, and the costs of eliminating gender gaps — and if so, exactly how?

Steve Stewart-Williams: I don’t think anyone argues that evolved facts have no ethical relevance. They just argue that the fact that something has an evolutionary origin doesn’t necessarily mean it’s good – or bad, or anywhere in between. That’s all I argue, anyway.

An example: It might be the case that, if a given sex difference has an evolutionary origin, it would be hard to eliminate, and that doing so would do more harm than good. As a result, we might decide that we shouldn’t try to eliminate it. But the reason for that decision wouldn’t be that the sex difference is natural; it would be that trying to eliminate it would do more harm than good. In other words, we’d be dealing with a consequentialist argument, not an argument from nature.

Importantly, this cuts both ways. If eliminating a socially constructed sex difference would do more harm than good, then we shouldn’t do that either, even though the difference isn’t “natural.” And if eliminating a natural difference would boost general well-being, we should do it despite its natural origins. In itself, the nature-nurture question is irrelevant to the ethical question.

We can turn the tables here as well: Why should we exclude certain facts from our ethical reasoning just because they happen to have an evolutionary origin? To do so is to risk falling prey to an anti-naturalistic fallacy!

What Skeptics Should Do

Nikil Mukerji: What could skeptical organisations such as the GWUP do to support work on evolutionary psychology? One project might be to investigate the charge that evolutionary psychology is pseudoscience. If one calls a real science pseudoscience, one is denying it legitimate scientific status. That’s a form of science denial.

Steve Stewart-Williams: I hadn’t thought about it exactly that way, but it is interesting. Some contemporary criticisms of evolutionary psychology echo arguments made earlier by critics of sociobiology such as Stephen Jay Gould, Richard Lewontin, Stephen Rose, and others.

I do think there’s genuine science denial around evolutionary psychology, and around behaviour genetics as well. Both fields posit genetic or evolutionary contributions to behaviour, which many people dislike. The difficulty is that, although there’s science denial on both the right and left side of the political spectrum,27 academia is predominantly left-leaning, and thus left-leaning forms of science denial are less likely to be labeled as such. In that way, politics can intrude on science and suppress it.

Nikil Mukerji: suggested a useful skeptical task: look at what critics are actually saying, systematise their assertions, test whether they are representative of the literature, and present the strongest version rather than a straw man. That matters because critics often respond: “Nobody actually believes that.” Skeptics need textual evidence.

For the GWUP, this could mean identifying the sources and authors behind the claim that evolutionary psychology is pseudoscience, building a bibliography, and analysing representative claims.

Steve Stewart-Williams: That sounds like a worthwhile project. You have to be fair and careful, but also willing to call science denial science denial when that’s what it is.

Nikil Mukerji: That is a good place for skeptics to stand: not on the side of a political tribe, but on the side of careful distinctions, fair evidence, and criticism that applies in every direction.

Steve Stewart-Williams: Exactly. Evolutionary psychology isn’t perfect. No science is. Some hypotheses have failed, and others will fail in the future. But to say that the whole field is worthless or pseudoscientific isn’t to give credit to what it’s achieved. The better approach is to examine claims one by one, ask what evidence supports them, ask what evidence could refute them, and keep moral questions separate from scientific ones.

Prof. Steve Stewart-Williams

Steve Stewart-Williams is a professor of psychology and the author of A Billion Years of Sex Differences: How Evolution Shaped the Minds of Men and Women. The book explores the extent to which some average psychological differences between men and women reflect evolutionary influences.

Follow Steve on Twitter/X for more psychology, evolution, and science.

Further Reading

I cover the question of sex differences in career choice in depth in A Billion Years of Sex Differences. In addition, I’ve written several academic papers with Lewis Halsey on the topic.

The main one is this 2021 paper in the European Journal of Personality:

• Stewart-Williams, S., & Halsey, L. G. (2021). Men, women and STEM: Why the differences and what should be done? European Journal of Personality, 35, 3-39. https://doi.org/10.1177/0890207020962326 [Free version]

This was published alongside two commentaries - one favorable; one critical.

• Ceci, S. J., Kahn, S., & Williams, W. M. (2021). Stewart-Williams and Halsey argue persuasively that gender bias is just one of many causes of women’s underrepresentation in science. European Journal of Personality, 35, 40-44. https://doi.org/10.1177/0890207020976778

• El-Hout, M., Garr-Schultz, A., & Cheryan, S. (2021). Beyond biology: The importance of cultural factors in explaining gender disparities in STEM preferences. European Journal of Personality, 35, 45-50. https://doi.org/10.1177/0890207020980934

Here’s our response to the critical commentary:

• Stewart-Williams, S., & Halsey, L. G. (2022). Not biology or culture alone: Response to El-Hout et al. (2021). European Journal of Personality, 36, 991–996. https://doi.org/10.1177/08902070211022477 [Free version]

From the Archive

Upgrade to a Paid Subscription

To help support my work, please consider upgrading to a paid subscription. A paid subscription will get you: (1) full access to all new posts and the archive, (2) full access to my “12 Things Everyone Should Know” posts, Linkfests, and other regular features, and (3) the ability to post comments and interact with me and the N³ Newsletter community.

On top of all that, you’ll be making it possible for me to take risks with the content I offer in the newsletter. I love being a psych prof, but I’m aware that some of the topics I write about - from the evolution of sex differences to the nature of intelligence to the excesses of wokeness - could potentially land me in hot water. Having the option to go full-time on Substack gives me the freedom and financial security to speak openly and honestly on any subject, without having to worry about being cancelled. So, by taking out a paid subscription, you’ll be helping support open and honest science writing.

Thanks!

Steve

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I’m very happy to report that I’ve just had an op-ed published in The Independent, titled “A Century of Evidence Tells Us Men and Women Are Different - Let’s Stop Pretending They’re the Same.” The piece summarizes some of the key arguments in my new book, A Billion Years of Sex Differences.

The road to publication was bumpier than I’d expected, ironically for reasons related to the very phenomenon the article highlights. Although the science of sex differences has advanced enormously over recent decades, discussing the topic remains contentious. Even modest, commonsensical claims can provoke strong reactions.

As I explain in the piece - and in the book - I got my first taste of this several years ago when I published an academic paper with Lewis Halsey about gender gaps in STEM professions. We argued that, although bias and barriers are part of the explanation, average sex differences in career-related interests and other relevant traits also contribute. I soon found myself at the center of an online controversy and was reported to my university’s equality, diversity, and inclusion office. Later I learned that the journal editor who handled the paper received calls from fellow academics to retract it - not due to errors or fraud, but as a way to censor the paper’s ideas.

To the credit of the university and the journal, nothing came of the complaints. But the episode drove home an uncomfortable truth: Talking honestly about sex differences is still a minefield.

The op-ed explores why that is, and why I think the controversy is misguided. Recognizing that men and women differ, on average, in certain traits is not incompatible with treating everyone equally and with respect. Indeed, if we care about improving people’s well-being, we have no choice but to follow the evidence wherever it leads.

Here’s a brief excerpt from the piece.

Why, then, does the topic generate so much heat? …

[One] reason is that many assume that generalisations about the sexes provide intellectual ammunition for sexism…

[But] we can’t just assume that differences imply deficiencies. As psychologist Diane Halpern observed, everyone agrees that men’s and women’s genitals are different, but no one would argue that either sex’s genitals are superior. The same applies to many psychological sex differences.

Indeed, it’s ironic that, in an age where we rightly celebrate differences and diversity, we often get outraged when anyone points any out. Not exactly tolerance of diversity!

Rather than supporting old-fashioned sexist views, the science of sex differences actively undermines them. It shows, for example, that there are no average sex differences in IQ (much to the surprise and disappointment of both sexes). And if either sex comes off worse, it’s men: men have higher rates of violence and criminality, for instance, and are more likely to abandon their children. Unless we think these are desirable traits, the science paints men in a less favourable light.

The larger point is that a commitment to equality doesn’t entail the denial of sex differences. We can treat men and women fairly and respectfully even if they’re not identical on every trait.

You can read the whole article here. And you can order A Billion Years of Sex Differences here.

Follow me on Twitter/X for more psychology, evolution, and science.

Further Reading

I cover the question of sex differences in career choice in depth in A Billion Years. In addition, I’ve written several academic papers with Lewis Halsey on the topic.

The main one - the one that ruffled a lot of feathers - is this 2021 paper in the European Journal of Personality:

• Stewart-Williams, S., & Halsey, L. G. (2021). Men, women and STEM: Why the differences and what should be done? European Journal of Personality, 35, 3-39. https://doi.org/10.1177/0890207020962326 [Free version]

This was published alongside two commentaries - one favorable; one critical.

• Ceci, S. J., Kahn, S., & Williams, W. M. (2021). Stewart-Williams and Halsey argue persuasively that gender bias is just one of many causes of women’s underrepresentation in science. European Journal of Personality, 35, 40-44. https://doi.org/10.1177/0890207020976778

• El-Hout, M., Garr-Schultz, A., & Cheryan, S. (2021). Beyond biology: The importance of cultural factors in explaining gender disparities in STEM preferences. European Journal of Personality, 35, 45-50. https://doi.org/10.1177/0890207020980934

Here’s our response to the critical commentary:

• Stewart-Williams, S., & Halsey, L. G. (2022). Not biology or culture alone: Response to El-Hout et al. (2021). European Journal of Personality, 36, 991–996. https://doi.org/10.1177/08902070211022477 [Free version]

From the Archive

Upgrade to a Paid Subscription

To help support my work, please consider upgrading to a paid subscription. A paid subscription will get you: (1) full access to all new posts and the archive, (2) full access to my “12 Things Everyone Should Know” posts, Linkfests, and other regular features, and (3) the ability to post comments and interact with the N³ Newsletter community.

Thanks!

Steve

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This post is an excerpt from my new book A Billion Years of Sex Differences. You can access the full collection here, or pick up a copy of the book here.

In this installment, we’ll see…

• Why mate preferences aren’t just products of evolution but causes of evolution as well

• Why the widespread idea that women are the sexual selectors in our species is only half true

• How men’s and women’s desires helped shape each other’s evolution

• How something as intangible as a preference can sculpt physical anatomy

• Why, when it comes to physical attractiveness, females in our species have the larger “peacock’s tail” - a reversal of the usual pattern in nature

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The last month has been a blur, as I’ve raced around the world promoting my new book, A Billion Years of Sex Differences. Among other things, I’ve given interviews to The Scottish Herald, Skeptiker magazine, and The Telegraph; recorded multiple podcasts; appeared at the HowTheLightGetsIn festival; and written an op-ed for The Independent. I’ve also received some behind-the-scenes pushback on the book. More on that later.

Last week was particularly hectic. I flew from London to Austin, Texas, to make my second appearance on ’s Modern Wisdom podcast, and to take part in a roundtable with Chris, , and Macken Murphy. Four hours of podcasting on four hours’ sleep - followed by my first ride in a self-driving car!

It’s all been great fun, but it hasn’t left me much time for Substack. So rather than rushing out something new this weekend, I thought I’d republish one of my favorite earlier posts: one I first published before many of my current subscribers came on board. I hope you enjoy it. Regular programming will resume next week!

Victimhood has always had a certain moral cachet. In recent years, however, it’s become one of the most powerful currencies in the social marketplace. Whereas people once sought status through highlighting their achievements, today they often do so by broadcasting their wounds.

The philosopher Bertrand Russell saw it coming. In a 1937 essay titled The Superior Virtue of the Oppressed, he warned of a growing tendency to see victimhood not just as a reason for sympathy, but as a badge of moral superiority. Since then, the trend has only accelerated.

Take Rachel Dolezal, the White woman who presented herself as Black and rose to a leadership position in the NAACP before her true ancestry was revealed. Or recall the actor Jussie Smollett, who staged a hate crime against himself by hiring two acquaintances to beat him up. These are baffling cases - until we recognize the powerful incentive, in today’s culture, of being a victim.

This isn’t to deny, of course, the reality of suffering or oppression. There are genuine victims in the world, and they deserve our compassion and support. However, when victim status becomes a path to prestige or power, it creates an unfortunate incentive for people to take on the victim role - sometimes unwittingly, sometimes strategically.

In this installment of the “12 Things Everyone Should Know” series, we’ll explore what the latest psychological research reveals about victimhood mentality: how it distorts perception, encourages bad behavior, and poisons intergroup relations.

You can access the full collection of “12 Things Everyone Should Know” posts here.

1. Victimhood as a Personality Trait

Psychologists have identified a personality trait they call the Tendency for Interpersonal Victimhood (TIV). It reflects a chronic sense of being wronged, and includes four key components:

1. Need for recognition - the desire to have one’s suffering acknowledged, validated, and empathized with

2. Moral elitism - a belief in one’s moral superiority, and the moral depravity of one’s opponents

3. Lack of empathy - obliviousness to other people’s suffering

4. Rumination - a tendency to obsess over problems, unpleasant experiences, and perceived slights

2. Victim Signaling as a Manipulation Tactic

Not every claim of victimhood is genuine. People with manipulative, narcissistic, or psychopathic tendencies sometimes weaponize victimhood: They exaggerate harm, fabricate grievances, and leverage sympathy to exploit other people’s better nature. As psychologist Adam Grant put it: “Constantly claiming to be a victim is not a sign of virtue. It’s a strategy for narcissists and psychopaths to get ahead.”

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I recently made my second appearance on Ricardo Lopes’ Dissenter podcast to discuss my new book, A Billion Years of Sex Differences. We had a fun, wide-ranging conversation about the science of sex differences, human nature, and some of the most contentious debates in contemporary psychology. Here are some of the topics we covered:

• Why I’m skeptical of the sex-gender distinction

• Whether parents shape sex differences

• Whether the science of sex differences is compatible with feminism

• The largest psychological sex differences in our species

• What drives the evolution of sex differences (hint: It’s not that sperm are cheaper than eggs)

• Sex differences in career-related interests

• Sex differences in cognitive abilities

• The trans phenomenon from an evolutionary perspective

• Three approaches to dealing with sex differences: gender-role traditionalism, gender-role progressivism, and gender-role individualism

Here’s a clip from the episode, where I discuss trans and nonbinary identification:

And here’s a clip where I discuss the three main approaches to dealing with sex differences, both as individuals and as a society:

The full episode is available on Apple Podcasts, Spotify, or wherever you get your podcasts. It’s also available on Ricardo’s Dissenter YouTube channel.

Buy A Billion Years now

Follow me on Twitter/X for more psychology, evolution, and science.

How You Can Support the Newsletter

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1. Like and Restack - Click the buttons at the top or bottom of the page to boost the post’s visibility on Substack.

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Steve Stewart-Williams

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In Case You Missed It…

• 12 Things Everyone Should Know About Wokeness

• The Evolutionary Enigma of Same-Sex Sexual Orientation

• Academia’s Leftward March

Psychology has always been influenced by the moral fashions of the time. In the age of “wokeness,” however, this process has gone into overdrive. According to a growing number of critics, psychology has become increasingly ideological, increasingly activist, and increasingly hostile to dissenting views.

But the counterrevolution seems to be gaining steam. More and more psychologists are pushing back against the woke turn in psychology, and trying to reclaim a more empirically based, more politically moderate, and less identitarian approach to the field.

In this post, I highlight some important recent examples of this pushback: three papers that explore and critique different aspects of the woke trend. Specifically, they look at the suppression of politically inconvenient findings, the erosion of public trust in psychology, and the growing tension between therapeutic practice and politicized conceptions of human suffering.

You might not agree with every claim made in these papers. But I hope you agree that they all raise important questions - questions we ignore at our peril.

1. Suppressing Science

The first paper examines what authors Stephen Ceci and Wendy Williams call the “dominant gender narrative”: the widespread belief that women face pervasive discrimination at every stage of their scientific careers. The paper argues that the strongest available evidence no longer supports this claim, but that researchers who point this out often face hostility or attempts at silencing, rather than open scientific debate. Here’s an excerpt from the piece.

The “dominant gender narrative” in science holds that bias against women is pervasive and occurs in every domain, including tenure-track hiring, letters of recommendation, awards, grants, journal publications, authorship assignment, citations, salaries, promotions, and teaching evaluations. Many of these claims are repeatedly broadcast despite their nullification by larger, stronger studies and meta-analyses that do not find gender bias. Because these stronger studies are cited less often, there exists a false belief among many faculty that gender bias is omnipresent in the tenure-track academy. As an example of this false belief, 248 U.S. faculty were surveyed about their beliefs regarding gender bias. They overestimated the extent of such bias in every domain. We illustrate this misalignment of beliefs by focusing on just one of the many domains in which bias against women is alleged but has been nullified by stronger studies: tenure-track hiring. We show that the dominant narrative of pervasive bias in favor of hiring men is not supported by the evidence. The reality is the opposite of what is believed, with women preferred over comparable men: multiple sources of evidence demonstrate that in tenure-track hiring in the United States and many European countries, women have an advantage over equally-accomplished men. Yet, the claim of bias against hiring women faculty continues to be widely cited in the premier science media. Challenging the gender narrative should be part of normal scientific discourse; however, doing so often evokes a backlash—as documented in testimonials by researchers who have been attacked.

I was one of the researchers Ceci and Williams contacted for testimonials, and I shared details of my own (relatively minor) experience of backlash. Specifically, I shared an excerpt from my new book, A Billion Years of Sex Differences, in which I discuss the heated reaction I received to a paper I wrote with Lewis Halsey about the causes of sex differences in STEM. Ceci and Williams quoted some of the excerpt in their piece, making it the first academic paper to cite A Billion Years.

Finally, we received a summary about the current state of affairs by Steve Stewart-Williams, an evolutionary scientist who conducts research on gender (Stewart-Williams, in press), that is worth repeating here:

“A vocal minority see positing sex differences as more than a mere social faux pas or difference of opinion, and view it instead as a moral transgression. For individuals in this camp, the idea that the sexes are naturally identical has become a sacred belief. Disagreement is seen not as an honest mistake or interesting challenge to be evaluated, but as sacrilege. And the typical response to sacrilege isn’t a tolerant appreciation of the wonderful diversity of human lifeways: ‘Well, I’m not personally into sacrilege, but if other people are, who am I to judge?’ Instead, the typical response is to censor, to silence, to cancel, punish, and shun.”

Citation: Ceci, S. J., & Williams, W. M. (2026). Organized dogmatism controls the message about gender bias in the academy. Journal of Controversial Ideas, 6, 4.

You can access the paper here for free.

The Nature-Nurture-Nietzsche Newsletter

The Truth About Sexism in Science

It’s an idea so widely accepted that we rarely think to question it: Women face rampant discrimination in science, while men coast along on a cushion of unearned privilege. You’ll hear this claim echoed everywhere, from the most prestigious scientific journals to the pages of…

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a year ago · 46 likes · 15 comments · Steve Stewart-Williams

2. The Cost of Woke Psychology

The second paper argues that psychology’s increasingly activist and identitarian public face may be undermining trust in the field. According to author Travis Proulx, many people - including many on the political left - feel alienated by the discipline’s moralizing tone, unrealistic worldview, and ideological conformity. The proposed remedy is simple: less moral grandstanding and more intellectual humility. As Proulx writes:

Given the predominant role of taxpayers in funding our research, we should be concerned that the voting public may justifiably perceive our science as emphasizing activist visions of what should be over the empirical complexities of what is. Ensuring public trust will depend on re-embracing persuasive intellectual humility and eschewing the identitarian vernacular and deficit model pedagogy that currently characterizes our public-facing messaging…

Psychologists know that public trust decreases to the extent that manifest ideological leanings diverge from their own. We also know that progressive activism within our science represents views that diverge from ≈90% of the Western public – including most left-wingers. Alarming, when roughly 90% of research funding ultimately derives from a public whose enthusiasm for funding scientific research decreases with perceived social distance from scientists. Western cultural institutions are moving on from monomaniacal identitarianism, re-embracing the intellectual humility to acknowledge that it depends. Will we join them in escaping this ‘identity trap’, or spiral into an ‘Endless Summer 2020’?

Citation: Proulx, T. (2026). An ‘outgroup’ public won’t trust a progressive ‘ingroup’ psychology. Current Opinion in Psychology, 70, 102316.

You can access the paper here for free.

3. How Victimology is Killing Therapy

The third and final paper focuses on cognitive behavioral therapy (aka CBT). Authors Richard Redding, Robert Maranto, and Nathan Honeycutt argue that therapists and clinical psychologists increasingly emphasize oppression and victimhood over personal agency - a shift they fear could undermine one of psychology’s most effective treatments, and make therapy less accessible to clients who don’t share progressive political views.

Cognitive behavioral therapy (CBT) rests on the premise that individuals possess personal agency to change their life circumstances. At the same time, given growing political homogeneity within psychology, views of individual agency are increasingly being displaced by greater emphasis on conceptualizing distress as reflecting systemic oppression. Drawing on research concerning these frameworks, this article briefly examines the implications of these trends for CBT in the United States. Specifically, we outline three potential concerns, including declining interest in traditional CBT, reduced value alignment between therapists and non-liberal clients, and possible shifts in the theoretical and practical focus of CBT. We conclude by discussing implications for graduate training and the importance of sociopolitical competence and diversity in clinical education…

It would be quite unfortunate if fewer young therapists are attracted to learning or practicing CBT, given its proven effectiveness. Or, if they corrupt it through a politicization that alters its fundamental approach, aims, and therapeutic strategies in favor of strategies that serve a political agenda. This will result not only in reduced therapeutic efficacy but in some cases therapy that is harmful or iatrogenic. It would also be unfortunate if politically moderate or conservative clients cannot find a therapist in their community who understands their values and problems or only one who practices a politicized form of CBT that is a very poor match for their sociopolitical values…

[W]e are hopeful that enough clinicians will “resist the ideological encroachment into the field to rebuff politicized narratives, to re-assert the primacy of individual clients in all their complexity.”

Citation: Redding, R. E., Maranto, R., & Honeycutt, N. (2026). Is the victimology worldview of many young therapists ill-suited for cognitive behavior therapy? Current Opinion in Psychology, 70, 102313.

You can access the paper here for free. Note that it’s part of a special issue in Current Opinion in Psychology focusing on identity and politicization in behavior therapy.

The Nature-Nurture-Nietzsche Newsletter

Social-Justice Therapy

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a year ago · 44 likes · 9 comments · Steve Stewart-Williams

Will papers like these be enough to turn the tide on wokeness in psychology? I’m not sure. But with the number of such papers growing steadily, I feel more optimistic today than I did when I had my own taste of ideological backlash five or so years ago.

Follow me on Twitter/X for more psychology, evolution, and science.

Related Reading From the Archive

How You Can Support the Newsletter

This post was free to read for all. If you like what I’m doing with The Nature-Nurture-Nietzsche Newsletter, and want to support my work, there are several ways you can do it.

1. Like and Restack: Click the buttons at the top or bottom of the page to boost the post’s visibility on Substack.

2. Share: Send the post to friends or share it on social media.

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3. Upgrade to Paid: A paid subscription gets you:

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If you could do any of the above, I’d be hugely grateful. The support of readers like you helps keep this newsletter going and growing.

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Steve