⬅️ Hub: Boy Crisis MOC
Developmental timing, brain differences, and biology.
Henrich, Chapter 8 — direct source for the “testosterone suppression system”
Henrich’s argument is an interaction among biology, role, and institution. In a longitudinal Cebu cohort, men who married and became fathers showed the largest four-year declines in morning testosterone; men who remained single declined least. Comparative cases from Lamu, the Datoga, and the Hadza are used to argue that pair-bonding, ongoing access to additional wives, paternal care, and local status competition can alter the pattern. The claim is therefore not that marriage chemically pacifies every man, but that institutions change how many men enter roles that recalibrate mating effort toward parenting and provision. testosterone as a mating-and-parenting system, PDF pp. 273–276 (file not included in this release) · Cebu longitudinal result, Figure 8.3, PDF pp. 276–278 (file not included in this release)
Testosterone is not a simple aggression, risk, or crime hormone. Henrich describes it as helping calibrate behavior to locally effective routes to status; in some settings it may support competitive effort rather than violence. The teamwork crossover in Figure 8.4 came from only 60 participants, and the wider hormone literature he cites contains small and mixed studies. Use the chapter to support plasticity and context—not biological determinism, a diagnosis of single men, or the claim that lower testosterone is always better. status, trust, and competitive behavior, PDF pp. 279–282 (file not included in this release) · within- versus between-group performance, Figure 8.4, PDF p. 281 (file not included in this release) · sample and interpretation qualifications, Chapter 8 endnotes, PDF pp. 567–568 (file not included in this release) · Chapter 8 source audit
Developmental timing and sex differences
- Boys are less resilient emotionally and mentally than girls. For example, father absence increases depressive symptoms in boys but not girls, and molested boys are 6-10 times more likely to commit suicide than girls.
- Girls mature faster biologically (e.g., prefrontal cortex development is 18 months ahead), exacerbating the maturity gap.
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.25 (file not included in this release)
The parts of the brain associated with impulse control, planning, future orientation, sometimes labeled the “CEO of the brain,” are mostly in the prefrontal cortex, which matures about 2 years later in boys than in girls. The cerebellum, for example, reaches full size at the age of 11 for girls, but not until age 15 for boys. Among other things, the cerebellum “has a modulating effect on emotional, cognitive, and regulatory capacities,” according to neuroscientist Gokcen Akyurek.
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.27 (file not included in this release)
The gender gap in the development of skills and traits most important for academic success is widest at precisely the time when students need to be worrying about their GPA, getting ready for tests, and staying out of trouble.
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.114 (file not included in this release)
After using MRI scans to examine sex differences in a sample of over 5,000 people in the UK—the largest study of its kind to date—psychologist Stuart Ritchie and his coauthors conclude that “for every brain measure that showed even large sex differences, there was always overlap between males and females: even in the case of the large difference in total brain volume there was 48.1% sample overlap.”3 In other words, the differences are dimorphic—different but overlapping—rather than binary.
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.115 (file not included in this release)
A large majority of the most aggressive people are male, but the differences in aggressiveness in the general population are much smaller. Second, these sex differences can be magnified or muted by culture. Some cultures valorize violence, while others do not.
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.115 (file not included in this release)
“Biology does represent the foundation of our personalities and behavioral tendencies,” writes Louann Brizendine in her book, The Female Brain. “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. If we acknowledge that our biology is influenced by other factors … we can prevent it from creating a fixed reality by which we are ruled.”4
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.115 (file not included in this release)
Third, these sex differences typically have a rather modest impact on day-to-day lives in the twenty-first century.
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.116 (file not included in this release)
There is always a danger of succumbing to the “naturalistic fallacy,” presuming that everything that is natural must necessarily be good. But nor is it helpful to deny or dismiss the reality of natural sex differences.
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.119 (file not included in this release)
Like aggression, risk-taking is one of the differences between male and female psychology that has clear roots in our evolutionary history. Taking risks must then make more sense for men. But why? Bluntly, because men are much less likely than women to reproduce at all. In fact, we have twice as many female ancestors as male ones.
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.120 (file not included in this release)
Psychologist Roy Baumeister makes the point more bluntly: “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.”23
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.120 (file not included in this release)
Men who are in danger of becoming evolutionary duds will be willing to take serious risks in order to gain access to a mate, perhaps by committing a crime to get more resources, or fighting in a potentially lucrative war. even a 50/50 chance of success looks pretty good to a man who is otherwise unlikely to have any children at all. As a result, Henrich writes, “Men’s psychology shifts in ways that spark fiercer male–male competition.”
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.122 (file not included in this release)
As a matter of biological fact, men are just lustier—or have what Konner labels more “driven sexuality”—than women.28 A comprehensive review of 150 studies found overwhelming evidence that men have a higher sex drive, “reflected in spontaneous thoughts about sex frequency and variety of sexual fantasies, desired frequency of intercourse, desired number of partners, masturbation, liking for various sexual practices, willingness to forego sex, initiating versus refusing sex, making sacrifices for sex, and other measures.”29 As Billy Crystal’s character says in the movie City Slickers, “Women need a reason to have sex. Men just need a place.”
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.125 (file not included in this release)
One striking example is the role of marriage, which Henrich describes, rather brutally, as “a testosterone suppression system.”45 (I’ve been almost continuously married for thirty years.) Testosterone levels are highest among young single men, and those with higher T are actually more likely to become fathers. But testosterone levels then fall among men who settle down with a wife and children, and the drops are sharpest among men who do more childcare. one group of scholars studying this evidence concludes that “human males have an evolved neuroendocrine architecture shaped to facilitate their role as fathers and caregivers as a key component of reproductive success.”46 There are broader social implications here too. As the institution of monogamous marriage spread, the number of men directly involved in raising families rose. The collective impact, via reduced testosterone levels, was to dramatically reduce overall levels of male violence. This is a good example of the complex interactions between biology, immediate environment, and broader culture.47
Related source — adult plasticity and fatherhood
Darby Saxbe on the science of fatherhood summarizes an interview about longitudinal paternal brain changes, caregiving-linked testosterone shifts, touch and play, paternal perinatal depression, and the interaction of biology, culture, and repeated care. It preserves the interview’s claims while flagging causal and measurement limits.
Of Boys and Men _ Why the Modern Male Is S - Reeves, Richard copy, p.127 (file not included in this release)
Human behavior is driven by a combination of nature (our instincts based in biology), nurture (the instructions we get from our surrounding culture), and agency (our personal initiative). Much of the drama of human life stems from the tension between these three forces.