I finished reviewing Richard Reeves‘s book, Of Boys and Men, with the tenth blog post on March 12. But I have been persuaded to allow Richard Reeves to speak directly to you in this video (thanks to Big Think) as a final summary. It is 15 minutes in length — a big ask of your time. If you have enjoyed or been intrigued by this series, Reeves’ words will add depth and “color.” Use the time stamps below to guide your access to his main points. 

Revisit My First Post?

It may also be worth it (good students as you are) to review my initial post (Of Boys and Men – Revisitation of a Crisis in Six Parts) as cliff notes for the subsequent nine posts. See a repeat of the book’s signature quotes below.

Richard Reeves Video by Big Think

Start: — Don’t write this book

1:20: — Reeves introduces himself and Of Boys and Men

1:29: — Three biggest challenges

1:50: — Men in education

2:35: — Girls are ahead in college

3:51: — Male and female brain development

5:17: — Education structured against boys

5:52: — Solutions for education

7:30: — Working-class men — “so busy leaning in, we don’t look down”

7:54: — Men in the workforce

9:20: — STEM and HEAL jobs (psychology potentially an all-female profession)

10:54: — Dad deficit

11:51: — Women’s economic independence – the greatest liberation in human history

12:33: — Male disadvantage becoming intergenerational

13:10: — Deaths of despair

13:36: — Male sense of purpose

13:50: — Last words: men as “worthless” or “useless”

Signature Quotes from Of Boys and Men

• “It is a bad idea to send a cultural signal to half of the population that there may be something intrinsically wrong with them.” (p. 108)
• “Masculinity is not a pathology; it is quite literally a fact of life.” (p. 108)
• “The rather boring truth is that masculine traits are more useful in some contexts and feminine ones in others, and neither set in intrinsically better than the other.” (p. 87)
• “By far the biggest difference is not how female and male brains develop but when.” (p.11)
• “For those on the political left, victim-blaming is permitted when it comes to men.” (p. 109)
• “Many conservatives deny the environmental science of climate change. But many progressives deny the neurosciences of sex differences.” (p. 111)
• “The real debate is not whether biology matters, but how much it does, and when it does.” (p. 87)
• “This is the most dangerous message of all: men are naturally different than women, but only in ways that are bad.” (p. 112)
• “Our estimates imply that the aversion to having the wife earn more than the husband explains 29% of the decline of marriage rate over the last thirty years.” (Marianne Bertrand, p. 37)
• “The idea of the provider is a major element in the construction of a masculine identity. It is a moral as well as an economic category.” (David Morgan, p. 34)
• “In sum, women mate horizontally and up (socioeconomically), and men mate horizontally and down.” (Scott Galloway)
• “In recent years, most of the scientists identifying natural differences have, if anything, tended to stress the superiority of women.” (p. 111)
• “The dominant narrative of gender equality is framed almost exclusively in terms of the disadvantages of girls and women.” (p. 72)
• “Given the huge progress made by women in recent decades and the significant challenges now faced by many boys and men, it makes no sense to treat gender inequality as a one-way street.” (p. 115)
• “Rather than looking in the rear-view mirror, we need to establish a new basis for fatherhood, one that embraces the huge progress we have made toward gender equality.” (p. 38)
• “Many people on the political Left seem to fear that even acknowledging the problems of boys and men will somehow weaken efforts for women and girls. This is entirely false as a matter of practice and creates a dangerous political dynamic.” (p. 115)
• “There is certainly very little evidence that women are paid less than men for doing the same work in the same way.” (p.26) Women are paid less because they do different work, or work differently, or both.” (p. 27)
• “But as long as men continue to be willing to put in long and often unpredictable hours, the prospects for structural reform [in career ladders] remain dim.” (p. 181)
• “The fact that the highest rungs [of the economic ladder] have male feet all over them is scant comfort for the men at the bottom.” ~ The Economist (p. xi)
• “Conservatives worried about boys and men need to be concerned about economic inequality. But liberals worried about inequality must pay more attention to boys and men.” (p. 72)
• “One study showed that a Black man without a criminal record is less likely to be hired than a similarly qualified white man with a criminal record.” (p. 55)
• “There is simply no way to reduce economic inequality without improving the fortunes of less advantaged boys and men.” (p. 61)
• “It’s not that gender equality discourages girls from pursuing science. It’s that it allows them not to if they’re not interested.” (Olga Khazan, p. 98)

Human males are more physically aggressive in all cultures at all ages.

~ Richard Reeves

The crisis of men and boys is exacerbated by a political narrative unwilling to acknowledge biological sex differences (What the Political Left Gets Wrong About Boys and Men- Part 3.1). By denying these differences, we cannot reform our educational curriculums to be fairer to boys or our places of work to be fairer to women. If we deny our biological differences, it will be harder for us to “reinvent fatherhood” and embrace the progress made toward gender equality. Given the gains made by women in recent decades and the significant challenges faced by men and boys, it makes no sense to treat gender inequality as a one-way street. Quoting Richard Reeves in my last post, “the rather boring truth is that masculine traits are more useful in some contexts and feminine ones in others, and neither set is intrinsically better than the other.”

Recognizing Biological Differences is a Radical Act

Recognizing and appreciating biological differences between the sexes has become a radical act in our current social-political milieu. Reeves was resistant to providing this counter-narrative but was confronted with the necessity to do so in addressing the crisis of boys and men. Evolutionary psychology, neuroscience, and sociobiology research have explored these issues for many years.

Biological Facts Don’t Deny or Suppress Sexual Preference or Gender Fluidity

Aside from the caveats to biological differences offered by Reeves in my last post, it must also be said: acknowledging basic biological facts does not deter acceptance and exploration of sexual preference fluidity or gender identities. Instead, it clarifies how evolution has built us to reproduce the species and adapt to different physical and cultural environments. For a more in-depth review of physical and behavioral differences between men and women, see Male & Female Biological Differences.

Biological Differences – Part 5.1

In my last post (Biological Differences Between the Sexes – Part 5.1), I described the differences between boys and girls related to the timing of their brain development. “By far,” says Reeves, “the biggest difference is not how female and male brains develop but when.” Boys’ brains develop more slowly, directly affecting their attention, self-regulation, and acquisition of skills and traits necessary for academic success.

Stress, Serotonin, and Aggressive Behavior

I also cited research that a stressful or unstable family environment appears to influence the capacity of the brain to metabolize serotonin. Serotonin helps to reduce aggressive behavior – and thus, a precarious home life would potentially cause boys to be more aggressive. The link between home life, serotonin, and aggression illustrates the interconnectedness of biology and “culture.”

Testosterone Has Significant Role in Behavioral Differences

This synergy of nature and nurture is further illustrated by how behavioral differences manifest between men and women — boys and girls — as a function of how androgens (testosterone) masculinize the brain. (See Appendix below.) Testosterone has a significant role in behavioral differences between the sexes related to aggression, risk, and sex drive.

Aggression, Risk, and Sex Drive

Sex differences in biology shape not only our bodies, including our brains, but also our psychology. We are not blank slates. Some of these differences are more about the timing of development rather than about the end results. But many differences are enduring. “Men are typically more aggressive, take more risks, and have a higher sex drive than girls and women,” says Reeves, reporting the research of Scott Kaufman. [1] Aggression, risk, and sex drive are co-mingled in sexual selection and reproduction. Behaviors of aggression, risk-taking, and sex drive are the most pronounced differences between men and women.

Aggression and Testosterone

One result of the testosterone bath of the male brain is a greater tendency toward physical aggression, not just in humans but in almost all primates and other mammals. Boys are five times more likely than girls to be frequently aggressive by the age of seventeen months! The gap widens until early adulthood before narrowing again. [2]

Testosterone and Aggression – It’s Complicated

According to Carole Hooven in Testosterone: The Story of the Hormone that Dominates and Divides Us, it looks like testosterone does not directly trigger aggression but instead amplifies it depending on the circumstances. The relationship between testosterone, masculinity, and aggression is complex. Reeves notes that most societies have become much less violent over time, and there are significant differences in crime rates among countries today. “That all these factors matter is not evidence that the relationship between T and aggression is weak,” Hooven writes, “rather it shows us that it’s complicated.”

Socialization and Biology Matter

Nobody denies that culture and socialization matter, and it would otherwise be difficult to explain the dramatic difference in levels of male violence between different places and eras. But Reeves adds, “it is equally silly to deny that biology matters here too, not least in the differences between men and women.”

Men Have a Greater Appetite for Risk

“The traits that get passed on are the reproductively effective ones, and that is what sexual selection is all about,” Reeves explains.

Men, for example, have a greater appetite for risk. Risky behavior is not a social construct; it can be identified in every known society throughout history, according to Joyce Benenson: Warriors and Worriers: The Survival of the Sexes.

“Sex differences exist in virtually every area in which risk has been studied,” Benenson reports, “with males engaging in more risk-taking than females – from hunter-gatherers to bank CEOs.”

Men Take More Risks Because of the Competition to Reproduce

Like aggression, risk-taking is one of the differences between male and female psychology rooted in our evolutionary history. Men in danger of becoming evolutionary duds will take serious risks to gain access to a mate — like committing a crime to get more resources or fighting in a potentially lucrative war. Men’s psychology shifts in ways that spark fierce male-male competition.

Reproductive Variance “Blows Your Mind”

Men take more risks because men are much less likely to reproduce than women. We have twice as many female ancestors as male ones. This difference between female and male ancestors is called “reproductive variance.” [3] DNA studies reveal that approximately 80% of women in human history have reproduced, compared to about 40% of men. This variance can take a minute to get your head around. Generally speaking, everyone must have a mother and father. But of course, one man can father many children with many women, while others father none at all. Genghis Khan, a direct ancestor of 1 in 200 people today, is perhaps the most famous example.

Math Problem of Too Many Men

To maximize reproduction, a culture needs all the wombs it can get, but a few penises can do the job. There is usually a penile surplus. ~ Roy Baumeister

Most human societies have been polygynous, allowing men to have multiple wives. You end up with what Harvard evolutionary psychologist Joseph Henrich calls the “math problem” of surplus men.

Men Will Risk to Save Others and Build Cities

Though male psychology is more wired for risk, antisocial forms of risk-taking (such as crime) occur only in circumstances of intense competition. Men are more willing to take risks to save others and do dangerous jobs (logging, construction, mining, fishing), which makes perfect evolutionary sense given the greater importance of female bodies for reproduction. We must be thankful for our (mostly male) firefighters, soldiers, and men who build skyscrapers. (Ninety-three percent of workplace fatalities were male in 2016, and 99.9% of military deaths are male.)

Courageous Acts by Men

Each year the Carnegie Hero Fund issues medals to civilians for courageous acts, specifically for risking their lives to save a stranger. In 2021, 66 of the 72 medals were awarded to men. As Margaret Mead wrote, “It is essential that the tasks of the future be organized [such that] dying for one’s country becomes unfeasible, and taking risks for that which is loved may still be possible” (Male and Female: A Study of the Sexes in a Changing World).

Men Are Just Lustier

Given that the differences between male and female psychology have emerged largely through sexual selection, it should be no surprise that the most significant difference between men and women is related to sex. As a matter of biological fact, men are just lustier and have, says anthropologist Melvin Konner, a more “driven” sexuality than women.” [4]

Female Drive and Sexual Motivation is Not as Strong

Occasionally there are articles by female bloggers asserting that the female sex drive is equal to a man’s. (It seems to be a badge of empowerment.) A recent one used evidence about rising female infidelity and described how women have a stronger “response desire” sexual motivation.

The phenomenon of “response desire” comes from Emily Nagoski, a sexuality expert and author of (Come As You Are). Nagoski disputes that sex exists as a “drive,” but she is clear that it is a motivational system in which men pursue with predominantly “spontaneous desire” and women operate primarily from “response desire” (See Spontaneous and Response Desire – the Underbelly of Heterosexual Mating.)

Response Desire is Evidence of a Less Robust Sex Drive

Response desire requires specific triggers (“a reason to have sex”) and a convergence of appropriate context to be guided into a sexual response. This is not proof of a stronger sex drive for women – quite the opposite. Response desire demonstrates a more complex and genuinely “weaker” sex drive that needs “jump-starts” out of a “neutral” gear. The spontaneous, initiating sexuality of a man is the essential condition of a higher sex drive. By definition, an always-ready spontaneous motivation for sex is “lustier’ than waiting for the right elements of context to provide a response motivation.

Using Nogaski’s research on response and spontaneous desire to make a case for a stronger female sex drive is a mischaracterization of her work.

Women Complain About Men’s Stronger Sex Drive Yet Dispute Its Existence

The fact that some women want to dispute that men have a stronger sex drive while also complaining about that very “lustiness” is silly and annoying. It is disrespectful to men to not accept the greater strength of the male sex drive as a biological fact, and it creates a pernicious double-bind for men when their sex drive is described pejoratively.

Acknowledging that men have a more robust sexual motivation system does not disempower women or denigrate their sexuality. Any logical analysis of sperm competition, male-on-male intrasexual competition, and reproductive variance would quickly reveal the evolutionary necessity of a more “muscular” male sex drive.

Evidence for a Stronger Male Sex Drive

As I have outlined in my blog posts and other writings, the evidence for men having a higher sex drive is shown in a review of 150 studies. Reeves summarizes some of this evidence, sourcing Roy Baumeister and colleagues. He could have also cited more recent work of Justin Lehmiller, Tell Me What You Want.

From Lehmiller, a higher male sex drive is evidenced by the following:

•  More spontaneous sexual thoughts
• More variety of sexual fantasies
• Greater power of visual triggers
• Desired frequency of intercourse
• Desired number of partners
• Frequency of masturbation
• Liking more varied sexual practices (in general)
• Unwillingness to forgo sex
• Initiating vs. refusing sex
• Making sacrifices for sex
• State of near-perpetual readiness
• Men pay for sex; women seldom do [5]

Women need a reason to have sex. Men just need a place.
~ Billy Crystal Character, City Slickers

Women Cheat for A Variety of Reasons

Women cheat on their partners for a variety of reasons unrelated to their sex “drive.” As relationship expert Esther Perel says (Mating in Captivity and The State of Affairs), “women are often looking more for a new self than a new partner.” (Also see Why Women Have Sex).

The Issue of Sexual Variety

Male sexuality generally seeks a variety of partners. Studies show that women may want more variety of sex with the same partner. But wanting more variety of sexual activities in a monogamous relationship just proves that women need more potent triggers for their sexual desire to be activated. Yes, more women are bored with the sex they are having. Men are not nearly as bored.

Another Way to Deny Biological Difference

Asserting an equal sex drive is another way for women and proponents of “progressive” politics to deny biological differences between the sexes. It is fueled by a false belief that a lesser aggregate sex drive somehow disempowers women in their quest for economic and political equality.

Evolutionary Reason for the Stronger Male Sex Drive

“There is a good evolutionary reason for this difference in sex drive. With a much higher chance of failing to father any children, men have had to be ready to take almost any opportunity for procreation,” says Reeves.

“Physically, men in their prime are hardwired to be in a state of near-perpetual readiness to couple with any female in their environment who is likely to conceive and bear children,” writes Marianne Legato, director of the Foundation for Gender-Specific Medicine.

In Conclusion – Connecting the Dots

How do biological differences between the sexes influence the crisis of boys and men?

• By denying biological sex differences, it is easier to see the causes of the boys and men crisis as individual and not structural.
• By denying biological sex differences, it is easier to believe that gender inequality only disadvantages women.
• By denying biological sex differences, the needs of boys and men can remain invisible and not worthy of remediation through social policy and civic initiatives.

How do differences related to aggression, risk-taking, and sex drive cause or exacerbate the crisis of men and boys?

• Expressions of aggression and risk-taking by boys can be misunderstood and inappropriately vilified in our schools.
• Expressions of aggression, risk-taking and sexual motivation by boys and men can be labeled as toxic. Masculinity is thus pathologized, sending a signal to half of the population that there is something intrinsically wrong with them. Solutions based on this perception will be inappropriate, if not counter-productive.

[1] Scott Barry Kaufman, “Taking Sex Differences in Personality Seriously,” Scientific American, (December 2, 2019).

[2] Baillargeon, R., et al, “Gender Differences in Physical Aggression: A Prospective Population-Based Survey of Children Before and After 2 Years of Age,” Developmental Psychology February 2007).

[3] Jason Wilder et al., “Genetic Evidence for Unequal Effective Population Sizes of Human and Females and Males,” Molecular Biology and Evolution (November 2004).

[4] Melvin Konner, Women After All: Sex, Evolution, and the End of Male Supremacy, 2016.

[5] About 1 million prostitutes are working in the US today. A study in New York found that opening a strip club or escort agency reduced crime in the surrounding neighborhood by 13%.

Appendix

Masculinizing the Brain

All humans start out as female. The Y chromosome of human males begins to masculinize the body during the first (prenatal) two months and the brain during the first trimester. Male brains in the second trimester are usually altered by exposure to androgens that influence psychological sex differences, predicting the degree and kind of postnatal play preferences (rough and tumble), personality traits, (thrill-seeking and aggression), and cognitive abilities (mental rotation). Psychological sex differences emerge before extensive gender socialization has taken place.

All human life stems from the reality of, and the difference between, men and women.

~ Nina Power – What do Men Want? Masculinity and its Discontents

In this series of posts about the boys and men crisis described by Richard Reeves (Of Boys and Men), I have detailed eleven problems and conditions faced by men and boys and fourteen solutions offered by Reeves to address these problems. One of Reeves’s most important contributions is “naming” and elucidating the “twelfth” problem of how the political Left and Right are unhelpful and wrong in their narratives about the crisis. He critiques the views about biological differences on both sides of the political spectrum. But it is the political Left that is most problematic in this arena.

Progressives Often Deny the Neuroscience of Sex Differences

As I said in Part 3.1 (What the Political Left Gets Wrong About Boys and Men) many progressives deny the neuroscience of sex differences. “For many progressives, it is now axiomatic that sex differences or behaviors are wholly the results of socialization,” Reeves laments. (Acknowledging biological differences between the sexes is not very “woke.”)

As part of its mission, Mating Straight Talk has criticized this “standard social science model (SSSM)”* and has described research of evolutionary psychology that incorporates natural selection and sexual selection in understanding the co-evolution of culture and biological adaptation.

Let’s Review Biological Sex Differences in the Next Two Posts

Because the political Left is so resistant to acknowledging biological sex differences, Parts 5.1 and 5.2 of this series will review some differences supported by research.

First — the Caveats About Biological Differences

The idea that there is a natural basis for sex difference is, however, politically charged. So, I’d better get the caveats in right away. ~ Richard Reeves

Reeves anticipated the degree of pushback he would get for acknowledging and researching biological sex differences. He went out of his way to soften the message with the caveats listed below. All these caveats are addressed and accepted by the discipline of evolutionary psychology and mate selection science (and in the website pages and blogs of Mating Straight Talk), except for Caveat #3.

Caveats Do Not Dilute Power of Average Differences

These caveats do not dilute the power of average differences between men and women that affect our relationships and culture. We can confirm the basic “rules” of our biology represented by the middle two-thirds of the bell curve while being curious about and honoring the exceptions to the rule.

Caveat #1: Differences are dimorphic but overlapping – rather than binary.

While certain traits are more associated with one sex than the other, the distributions overlap, especially among adults. For every brain measure that showed significant sex differences, there was always an overlap.

For example, the typical male is more willing to take risks than the typical female (especially in adolescence). But some women are more risk-taking than some men. A large majority of the most aggressive people are male, but the differences in aggressiveness in the general population are much smaller.

Caveat #2: Sex differences can be magnified by culture.

The immediate environment and broader culture affect how these biological differences develop and are expressed. Sex differences can be magnified or muted by culture. Culture and biology do not develop separately from each other. They co-evolve.

“It is hard to find a responsible scientist who is either an outright determinist or an outright denier on the question of biology,” says Reeves.

But Reeves identified outright deniers in an earlier section of the book. Denial of biological differences was, for Reeves, a significant motivation for writing this book.

Neuroscientist Lou Ann Brizendine (The Female Brain and The Male Brain) writes: “Biology does represent the foundation of our personalities and behavioral tendencies. If, in the name of free will and political correctness, we try to deny the influence of biology on the brain, we begin fighting our own nature.”

Yet, as British neurobiologist Gina Rippon explains, “it is perfectly possible to believe in biology without mindlessly assuming that human nature is fixed and unchangeable or that culture and environment are irrelevant.”

Caveat #3: Sex Differences have a modest impact on our day-to-day lives.

Reeves claims sex differences typically have a modest impact on day-to-day lives in the twenty-first century. He says there is more room for other drivers of behavior. Reeves supports a three-part model of human behavior: a combination of nature (our instincts based on biology), nurture (the instructions we get from our surrounding culture), and agency (our personal initiative.) This model is an excellent starting point for understanding our behavior. No doubt, much of the drama of human life stems from the tension between these forces.

Disagreement About the Impact of Sex Differences

I argue two things related to this caveat: 1) the impact of sex differences is more than “modest” in our daily lives, and 2) culture and personal agency are interdependent with sex differences, not separate from them.

To the first point: biological sex differences have a powerful impact on our current cultural milieu – on the tone of our near-ubiquitous conversations about gender identity and sexual preference. Sex differences are revealed and impact dozens of dating apps, dating websites, dating reality television shows, and relationship coaching. It is the water that flows in nearly all cinema and literature. The difference between the sexes frames conversations about “consent” in heterosexual relationships and fuels the search for an antidote to “toxic masculinity” – and ultimately, the recovery (or creation) of “noble” masculinity that provides much needed servant leadership.

Modest impact? Hardly. Whenever or wherever sexuality is involved (especially heterosexuality) – biological sex differences are salient; the impact on our daily lives is quite significant.

Caveat #4: Average sex differences do not justify the institutionalization of gender inequality.

“There is a fear that biology can be used to prove an intellectual foundation for sexism,” says Reeves. “This is well-founded given our history; it can be used to justify oppression.” Reeves does not elaborate on the historical data points of such oppression. But goes on to emphasize a thought not repeated often enough:

Denying science altogether is not useful. The rather boring truth is that masculine traits are more useful in some contexts and feminine ones in others, and neither set in intrinsically better than the other.

Reeves’s point about the institutionalization of gender inequality is well understood and accepted by credible researchers in sociology, anthropology, neuroscience, biology, and evolutionary psychology. There is no argument here, but the caveat apparently needs to be said, especially given the pernicious nature of our gender-related culture wars.

Caveat #5: Average differences between groups should not influence the view of individuals.

We should not view individuals by assumptions of aggregate difference. This caveat is obvious; it is not disputed among scientists who understand subject sampling, statistical analysis, and the range within the bell curve of individual differences.

Naturalistic and Moralistic Fallacies

Evolutionary psychology has directly addressed the problem of making assumptions about an individual based on data of aggregate difference. Because of general resistance to evolutionary psychology in some social sciences circles, the academic literature emphatically cautions against succumbing to two fallacies of reasoning.

The first is the naturalistic fallacy. This fallacy presumes that everything natural is necessarily good. That is a leap of logic not supported by evolutionary psychologists.

More problematic is the other fallacy lurking around the resistance to evolutionary psychology – the moralistic fallacy. The moralistic fallacy says what is good, or moral, ought to be true and is found in nature. This fallacy is more familiar to the political Left, such as “men and women ought to be given equal opportunities because women and men (in aggregate) can do everything equally well.”

Sex Differences in Brain Development

If, in the name of political correctness, we try to deny the influence of biology on the brain, we begin fighting our own nature. ~ Louann Brizendine (The Female Brain)

Boy’s Brains Develop More Slowly.

Boy’s brains develop more slowly, especially during the most critical years of secondary education. The parts of the brain associated with impulse control, planning, and future orientation are primarily in the prefrontal cortex, which matures about two years later in boys than in girls. As a result, almost one in four boys is categorized as having a “developmental disability,” according to a study in Pediatrics (2017).

Attention and Self-Regulation

The cerebellum reaches full size at age 11 for girls but not until age 15 for boys. The cerebellum has a modulating effect on emotional, cognitive, and regulatory capacities. The most significant difference between boys and girls related to attention and self-regulation occurs during middle adolescence.

Adolescent Male Brains Have More Accelerator and Less Brake

Adolescence is a period when it is harder to restrain ourselves. It is a battle between the sensation-seeking part of the brain (Go to the party! Forget school!) and the impulse-controlling part (I really need to study tonight). “It helps,” says Reeves, “to think of these as the accelerator and brake pedals in a car.” Boys have more acceleration and less braking power.

Adolescent Girls Have More Synapses and Connectivity

“In adolescence, on average, girls are more developed by about 2-3 years in terms of the peak of their brain synapses and their connectivity processes,” says Frances Jensen, chair of the department of neurology at the University of Pennsylvania’s School of Medicine. This is no surprise to most people who know 15-year-old boys and girls.

Gender Gap In Skills and Traits

The gender gap in developing skills and traits most important for academic success is the widest at precisely the time when students need to worry about their GPA, getting ready for tests, and staying out of trouble. According to a 2019 National Academies of Sciences, Engineering, and Medicine report, “sex differences in associations between brain development and puberty are relevant for understanding prominent gender disparities during adolescence.”

The Biggest Difference is When Development Occurs

“There are certainly some biological-based differences in male and female psychology that last beyond adolescence,” Reeves explains. “But by far, the biggest difference is not how female and male brains develop, but when.”

Nature and Nurture (Culture) on Sexual Psychological Difference

The real debate is not about whether biology matters, but how it does and when it does. ~ Richard Reeves

According to Reeves, culture determines how we manage, channel, and express many natural traits (see Caveat #2 above). As has been said, both nature and nurture determine how biological differences will manifest and express themselves.

Serotonin, Aggression, and Unstable Environment

For example, growing up in a stressful or unstable family environment appears to influence the capacity of the brain to metabolize serotonin. Serotonin helps to reduce aggressive behavior. If a boy or man does not metabolize serotonin effectively, their behavior may be more aggressive.

Boys with “Sensitive Genes” Do Worse When Fathers Leave

Significant research in epigenetics identifies how gene expression can sometimes be turned on or off. Reeves reports that boys with genes sensitive to the environment do worse when their biological fathers leave the household and benefit if their father stays or rejoins the family.

Harvard evolutionary psychologist Joseph Henrich argues that it makes the most sense to think of the co-evolution of nature and nurture. “Culture rewires our brains and alters our biology,” he says, “without altering the underlying genetic code.”

Marriage is a Testosterone Suppression System

Henrich says that marriage is a “testosterone suppression system.” Testosterone levels are highest among young single men, and those with higher testosterone are more likely to become fathers. But testosterone levels fall among men who settle down with a wife and children, and the drops are sharpest among men who do more childcare. “Human males have an evolved neuroendocrine architecture shaped to facilitate their role as fathers and caregivers as a key component to reproductive success,” says Henrich.

The Nice Guy – Bad Boy Trade-off

Falling testosterone levels mean that a caregiving “nice guy” (wanted and yet not wanted by many women) has less “bad-boy power” at the neuroendocrine level. Given the common problem of “hedonic adaptation”** or boredom inside a monogamous partnership, it is doubly hard for “nice” husbands and boyfriends to compete with fantasies about “bad boys” outside the pair bond. Luckily, one might say, it is good that women tend to turn down their (already lower) sexual interest when in monogamous partnerships.

No Wonder Married with Children Means Less Sex

Directing the energy required to raise children often has the practical effect of reducing female sexual desire. When you match that with lessened male testosterone, it is no surprise that many married couples with children have a diminished sex life. Lower testosterone and mutually reduced sex drive may not be a bad thing; it may be an evolutionary adaptation for successful caregiving and parenting.

Nature and Nurture Interdependence – Proximate or Ultimate Causation?

As outlined in my previous writing and summarized by experts in evolutionary psychology and sexual selection, the issue here is about identifying proximate causes for human (or animal) behavior versus ultimate causes. Proximate causes are influences from the current environment and culture. Ultimate causes are the result of thousands of years of human adaptation.

Survival and sexual reproduction operate almost entirely by ultimate causation. That is the starting point, the infrastructure, for any exception or adaptive readjustment that may come from the current environment or culture.

There Are Limits to Evolution as a Function of Culture

There is evidence of epigenetics — the effect of environmental factors on gene expression. Cultures do indeed change, and cultures can determine how some elements of masculinity and femininity are expressed.

But, as some anthropologists and evolutionary psychologists have said, there are limits to the evolution of human behavior as a function of culture. Humans are never going to grow wings and fly around the sky.

Can We Evolve Beyond Sex for Protection and Resources?

How quickly can we evolve from a “sex traded for protection and resources” (safety and security) paradigm? Perhaps we are doing that right now… but sexual desire operates with ancient hormonal roots and physiological signals of fertility. Don’t hold your breath for this evolutionary change. Biological differences between the sexes have been around for a long time.

*The Standard Social Science Model (SSSM) is a model of human development that assumes the mind was shaped primarily, if not entirely, by culture and social conditioning. SSSM is often associated with the concepts of “blank slate,” social constructivism, or cultural determinism that have dominated the social sciences throughout the 20th century (especially in the U.S.).

**Hedonic adaptation is the observed tendency of humans to quickly return to stable levels of happiness despite positive or adverse events. In a romantic context, it means that humans might “get used to” their partner and not sustain initial levels of excitement and passion over time.