Dads who take testosterone supplements while becoming fathers may be actively suppressing the biological rewiring that makes them good parents — and their partners' anecdotal reports back that up.
Modern Wisdom
Dads who take testosterone supplements while becoming fathers may be actively suppressing the biological rewiring that makes them good parents — and their partners' anecdotal reports back that up.
TL;DR
Dr. Darby Saxbe, USC clinical psychologist and fatherhood researcher, unpacks the science of "dad brain" — the measurable neurological, hormonal, and psychological changes men undergo when they become caregiving fathers. Dads who are hands-on lose roughly 1% of gray matter volume (vs. 2.5% in moms), gain empathy circuitry, and see testosterone drop — all tied directly to time spent caregiving, not mere biological fatherhood [1] — Darby Saxbe "Dads who are hands-on lose about 1% of gray matter volume — mostly in the cortex — a change entirely driven by parenting time, not the mere…" 01:03 . One in ten new dads experiences postpartum depression, yet the condition goes largely unrecognized [2] — Darby Saxbe "10% of new dads get postpartum depression: Approximately 10% of new fathers experience depressive symptoms during the perinatal period, rou…" 1:03:03 . The single most useful takeaway: paternal involvement isn't just good for kids — it measurably protects moms' mental health too [3] — Darby Saxbe "The brain changes in new dads happen almost entirely in the mentalizing network — the seat of empathy and mind-reading. It grows because ca…" 24:24 .
Dr. Darby Saxbe, USC clinical psychologist and author, explores the neuroscience, hormonal changes, and psychological costs of fatherhood — including dad brain, paternal postpartum depression, and how hands-on caregiving literally rewires the paternal brain.
Darby Saxbe walks through the quantitative differences between maternal and paternal brain remodelling. New mothers lose around 2.5% of gray matter volume across the entire brain — including subcortical structures like the amygdala, ventral striatum, and other regions linked to hormones, reward, and gut feelings. [1] — Darby Saxbe "1% gray matter loss in dads: Hands-on fathers lose approximately 1% of gray matter volume across the transition to fatherhood, mostly in th…" 01:43 Fathers, by contrast, lose approximately 1% and the changes are confined primarily to the cortex, which governs executive functioning and reasoning. Crucially, Saxbe's lab found that paternal brain change is entirely tied to parenting behaviour: dads who felt more bonded prenatally, who took more time off after birth, who spent more daily time with their babies in the first months, and who reported greater pleasure in parenting showed the biggest brain changes. The implication is radical — simply being a biological father is not sufficient to rewire the paternal brain.
Darby Saxbe frames the modern father's transformation with historical sweep. By some estimates, dads today spend three to four times more daily time parenting than their 1950s counterparts, with millennial dads at record levels and Gen Z dads pushing higher still — a shift accelerated by the pandemic's forced co-parenting experiment. [1] — Darby Saxbe "Dads' parenting time tripled or quadrupled: By some estimates, dads' daily parenting time has tripled or quadrupled compared to fathers in …" 02:23 To explain why paternal roles are so culturally variable, Saxbe introduces two contrasting African hunter-gatherer societies. The Aka of the Congo practice cooperative net hunting as couples, which makes strict role specialisation economically illogical — fathers spend extensive time within arm's reach of infants as a result. Just one day's drive away, the Kipsigis prohibit fathers from even picking up babies in their first year, believing a father's masculinity would compromise an infant's development. These examples make the point that there is no universal model of fatherhood — roles track closely with how a society generates its resources.
Long before the baby arrives, the transition to fatherhood is already underway. Saxbe describes a cluster of changes in expectant fathers: hormone shifts, heightened anxiety, couple relationship strain, and sleep disruption that begins during pregnancy itself. Her neuroimaging study began mid-pregnancy, which she acknowledges may mean some brain changes were already underway — a limitation she would correct with earlier scans given more funding. The conversation turns to an arresting finding from her own lab: couples who engaged in more negative conflict during pregnancy experienced more medically complex and risky births, with both partners rating the birth as more stressful. [1] The mechanism, Saxbe explains, is physiological — stress and tension physically impair the relaxation required for effective labour, making emotional relationship health a literal obstetric variable.
The presence of fathers in the delivery room is a relatively recent phenomenon — it only became normalised in the 1960s and 70s, and even today it generates controversy every sports season when athletes miss games for the birth of a child. Saxbe argues it is genuinely valuable when the couple communicates well and the father can provide calm support, but can be actively harmful when dads are terrified and unprepared — partly because contemporary dads are filling a social support role that used to be shared across extended female kin networks. The discussion then moves to couvade syndrome, the claim that men experience phantom pregnancy symptoms. Saxbe is sceptical of the strong version of the claim, noting her lab found no hormonal associations with self-reported symptoms; most are likely stress-related manifestations like gastrointestinal distress and insomnia.
The presence of fathers in the delivery room is a relatively recent phenomenon — it only became normalised in the 1960s and 70s, and even today it generates controversy every sports season when athletes miss games for the birth of a child. Saxbe argues it is genuinely valuable when the couple communicates well and the father can provide calm support, but can be actively harmful when dads are terrified and unprepared — partly because contemporary dads are filling a social support role that used to be shared across extended female kin networks. The discussion then moves to couvade syndrome, the claim that men experience phantom pregnancy symptoms. Saxbe is sceptical of the strong version of the claim, noting her lab found no hormonal associations with self-reported symptoms; most are likely stress-related manifestations like gastrointestinal distress and insomnia.
Saxbe is unambiguous that having a baby reliably reduces relationship satisfaction — not because love disappears, but because the practical demands of new parenthood are genuinely brutal. She frames it memorably: she and her husband went from 'good time pals' to running a small business with a very disappointed customer who cries around the clock. [1] — Darby Saxbe "I used to joke that my husband and I went from good time pals to we're suddenly operating a small business with a very disappointed custome…" 16:13 She advises couples to prioritise learning to communicate effectively, especially around birth preparation — men rarely hear birth stories or see realistic birth portrayals, leaving them woefully unprepared for what labour actually looks like. The segment ends with a pointed warning: if you think having a baby will fix your relationship, you are gravely mistaken.
The central mechanism of dad brain is one of the episode's most striking insights: biology requires behaviour. Mothers arrive at birth with their caregiving dial already turned all the way up — incubating a pregnancy costs thousands of calories and hard-wires the investment. Fathers' dials sit in the middle by default, available to rise or fall based on local demands. Saxbe introduces the concept of facultative adaptation to describe this: a biological capacity that only comes online when activated by the environment. [1] — Darby Saxbe "Mother's caregiving drive is turned all the way up at birth — incubating a pregnancy costs thousands of calories and locks in that investme…" 18:06 She draws on paternity uncertainty as an evolutionary explanation for fathers' more conditional attachment — uniquely among primates, humans conceal ovulation, incentivising men to pair bond and invest across multiple visits rather than helicopter in for a single encounter. The stability of the relationship with the mother, Saxbe adds, further modulates a father's predilection to caregive.
The trade-offs of parenthood extend into a surprising long-term benefit: having children appears to be neuroprotective. Saxbe cites UK Biobank data from middle-aged and older adults showing that people who have had more children have better cognitive functioning and brains that machine-learning algorithms rate as chronologically younger — with the effect plateauing at around 3 children. [1] — Darby Saxbe "More kids = younger-looking brain: UK Biobank data shows that having more children (up to about 3) is associated with better cognitive func…" 28:41 The finding holds for both mothers and fathers, which Saxbe takes as evidence that the mechanism isn't pregnancy hormones, breastfeeding, or birth experience — it's social integration. Being closely and durably connected to other people is one of the strongest predictors of brain health, and children are an unusually powerful forcing function for that connection. The conversation briefly explores whether intense friendship or pet ownership might replicate the effect, with Saxbe allowing that deep empathetic caregiving of any vulnerable creature could potentially deliver similar brain benefits.
A short detour into cultural testimony: Chris Williamson plays a clip of actor Bob Odenkirk articulating what many new fathers feel but struggle to express. [1] — Bob Odenkirk "I didn't have to ask myself, what am I doing here? How can I be meaningful today? I didn't have to ask that question because the fucking an…" 32:48 Odenkirk describes being deeply jealous of parents with young children at home, because those years provided him with total clarity of purpose — no existential questions about meaning or contribution, just the concrete daily work of getting kids to school and having a laugh with them. Darby Saxbe connects this to research showing that sense of meaning, coherence, and connectedness are among the most powerful drivers of psychological wellbeing, and that fatherhood is one of the most reliable delivery mechanisms for all three.
The 'deadbeat dad' narrative is partly true and largely oversimplified. Saxbe charts the data: in 1960, 88% of American kids lived with a father at home; that fell to a nadir of 67% in 2005 before rebounding to around 76% today — a U-shaped trend that the binary absent/present framing entirely misses. [1] — Darby Saxbe "Father presence rebounded to 76%: Father presence in US homes dropped from 88% in 1960 to 67% in 2005, but has since rebounded to about 76%…" 33:51 Many non-residential fathers are deeply involved in caregiving; the real variable is the degree of engagement, not a simple presence or absence. Saxbe makes the point personal, describing how her own parents' divorce led to her father transitioning from a relatively hands-off caregiver to a fully primary parent on alternating weeks. She closes the segment with the story of a man who spent 3 years in jail during his son's early childhood, reconnected through parenting classes, and now directs a Project Fatherhood programme at Homeboy Industries in LA — a testament to the dial's ability to be turned back up at any point.
The hormonal dimension of fatherhood is as well-documented as the neurological one, and Saxbe walks through it with the challenge hypothesis as the organising framework. [1] — Darby Saxbe "The challenge hypothesis explains that testosterone rises during mating competition and then adaptively falls when the strategy shifts from…" 39:38 Testosterone rises during mate competition — maximising opportunities to reproduce — and then adaptively falls once mating is accomplished and the strategy shifts from quantity to quality of offspring. The pattern holds across birds, rodents, primates, and humans. In new fathers specifically, the testosterone drop is linked to caregiving behaviour, not simply to the existence of a baby. The downstream effects are broadly health-protective: less risky driving, fewer fights, lower substance use, more attention to health checkups, greater investment in the pair bond. Saxbe and Chris discuss the irony of men who supplement testosterone in an attempt to signal masculinity, potentially suppressing the very adaptive shift that makes them effective fathers — with anecdotal reports from mothers suggesting the connection is real.
The testosterone conversation reaches its philosophical core: what is masculinity actually for? Saxbe's answer is unambiguous — not a hormone level, but a social role. [1] — Darby Saxbe "I would argue that being a good dad is one of the most manly things you can do. You're literally rearing the next generation. You're guidin…" 47:35 Being a good dad means guiding, protecting, inspiring, and teaching the next generation; that is, she argues, what masculine capacity is evolutionarily designed for. Maintaining artificially high testosterone while suppressing the natural adaptation to fatherhood is, as Chris Williamson puts it, a 'horrendous own goal' that risks ending your lineage in the name of signalling the very thing it destroys. The conversation broadens to the parallel pressure on mothers — the 'bounce back after baby' culture that treats parenthood as an inconvenience to be reversed rather than a transformation to be embraced — and Saxbe's view that contemporary society catastrophically under-values caregiving as a public good.
Does the neurological transformation of parenthood reset and recur with each new child? A Dutch study of second-time mothers provides a first answer: yes, but differently. [1] — Darby Saxbe "Brain change is U-shaped with more kids: Research from the Netherlands shows that maternal brain gray matter shrinks again with a second ch…" 51:30 The brain shrinks again, but in regions associated with managing multiple simultaneous inputs and task-switching rather than the same areas as the first time — precisely the cognitive skills needed to parent more than one child. Saxbe describes this as a U-shaped pattern overall, with volume loss followed by partial recovery and then another targeted loss. Chris poses the natural question about twins and triplets, which Saxbe finds genuinely fascinating: twin parents likely get a double-dose of parenting neurochemistry and may speedrun the second-child brain adaptation from birth, while also forcing greater paternal involvement simply out of necessity.
In a paper her lab literally completed over the previous weekend, Saxbe reveals a striking and somewhat uncomfortable finding: the daughter effect runs in an unexpected direction. [1] — Darby Saxbe "Dads with daughters: more T drop, more stress: Darby Saxbe's lab found that new fathers of daughters show a larger drop in testosterone, sp…" 53:31 Fathers of daughters show a larger testosterone drop, spend less time caring for babies, and report more parenting stress and worse bonding in the first six months — compared to fathers of sons. Saxbe's hypothesis, which Chris Williamson arrives at independently, is that dads default to proprioceptive, rough-and-tumble, physically activating play styles that feel natural and intuitive with baby boys but less so with baby girls. Parental cognitions about children's character are also shaped by known sex before birth — girls are described as delicate and sweet, boys as rambunctious and tough — which may set up different default interaction patterns from day one. An Emory University study adds neurological detail: fathers' brains show differential responses to daughters' happy faces versus sons' distressed expressions.
Saxbe's own graduate research offers a window into the physiological mechanics of modern domestic life. Following dual-income couples for a week across their LA homes, she found that housework time in the evenings correlates with less cortisol drop at bedtime — a disruption of the normal diurnal rhythm that governs stress recovery. [1] — Darby Saxbe "Housework impairs cortisol recovery: More time spent on housework in the evenings was associated with less cortisol drop at bedtime, sugges…" 1:00:52 Interestingly, the cortisol data also broke along gender lines: moms' recovery benefited when dads did more housework, while dads' recovery benefited when they had more leisure time. The follow-on finding is stress contagion — cohabitating couples have measurably linked cortisol levels, and when relationship quality is poor, that linkage tightens in a destructive direction. Partners in high-conflict relationships amplify each other's stress rather than buffering it; the solution, she argues, is teaching couples to fight in ways that de-escalate rather than escalate.
The episode's most contentious and socially urgent segment. Saxbe confirms that depression in new fathers runs at roughly twice the general population rate — about 10% — and shares all the same risk factors as maternal postpartum depression: sleep deprivation, relationship conflict, identity disruption, hormonal and neurological upheaval. [1] — Darby Saxbe "About 10% of new fathers experience depressive symptoms in the perinatal period — roughly twice the general population rate. The risk facto…" 1:02:20 She prefers the term 'perinatal depression' as gender-neutral but acknowledges the cultural minefield. Chris plays a TikTok video in which a British father describes struggling to bond with his daughter and eventually being diagnosed with postnatal depression — followed by a stream of dismissive, gatekeeping comments from women insisting this isn't real or isn't theirs. The exchange triggers one of the episode's sharpest exchanges: Chris argues that denying men's postpartum depression harms not just fathers but mothers and children directly, since the best predictor of maternal mental health is the support she receives from her partner. Saxbe connects the dots: you cannot demand full paternal involvement and simultaneously deny that involvement has mental health consequences.
Saxbe's evolutionary explanation for postpartum depression is both clarifying and damning of modern social organisation. Humans are cooperative breeders: we evolved to raise children embedded in kin networks where care was distributed across dozens of people. In hunter-gatherer societies, becoming a mother typically increased a woman's social integration. In contemporary society, it often triggers the opposite — isolation from public life, exclusion from workplaces, and loss of the communal fabric that buffered the transition. [1] — Darby Saxbe "Humans evolved as cooperative breeders — new mothers were embedded in kin networks that shared care. In contemporary society, new parents a…" 1:15:39 The US has no universal paid parental leave, many shift workers return to work within two weeks of birth, and public spaces are often hostile to infants. Without this structural support, the universal human vulnerability to new-parent stress tips into clinical depression. Saxbe notes that depression in general appears largely absent from hunter-gatherer societies, lending further weight to the mismatch hypothesis.
The practical intervention session of the episode. Saxbe explains that postpartum depression is correlated within couples — depressed dads make depressed moms more likely, and vice versa — but a well partner is also a powerful protective buffer. [1] — Darby Saxbe "A Swedish paternity leave reform created a natural experiment: babies born right after expanded paternity leave was introduced had mothers …" 1:21:30 The most evidence-backed interventions centre on social integration: proactively mapping who can help with what, overcoming the cultural conditioning toward self-reliance, and leaning into community. Her lab leads psychoeducation workshops with a hospital system serving low-income new parents, walking them through social support mapping before the baby arrives. The Swedish paternity leave reform provides a rare natural experiment: babies born right after expanded paternity access was introduced had mothers who filled significantly fewer anti-anxiety prescriptions. The single clearest policy lever for maternal mental health, Saxbe argues, is giving fathers the time and permission to be present.
The episode closes on a practical and philosophical high note. The worst advice Saxbe encounters is the myth that fathers have nothing to contribute in the early months — a belief that actively discourages precisely the hands-on caregiving that builds paternal brains, cements bonds, and protects maternal mental health. [1] — Darby Saxbe "The most damaging advice new dads receive is that they're biologically useless in early infancy and should step back. This myth drives fath…" 1:23:16 She also cites Richard Reeves' argument that paternity leave should be available far beyond infancy — up to a child's 14th or even 18th birthday — recognising that different stages of childhood require different kinds of paternal presence. The conversation turns to the broader cultural failure of self-optimisation culture, which celebrates solitary biohacking routines but ignores the relational skills most associated with long-term wellbeing. Saxbe closes with a note on longevity research: socially isolated men in late life face dramatically elevated mortality risk, and learning to care for others — beginning with your own children — is one of the most powerful protective investments a man can make.
Chapter 1 · 00:19
Darby Saxbe walks through the quantitative differences between maternal and paternal brain remodelling. New mothers lose around 2.5% of gray matter volume across the entire brain — including subcortical structures like the amygdala, ventral striatum, and other regions linked to hormones, reward, and gut feelings. [1] — Darby Saxbe "1% gray matter loss in dads: Hands-on fathers lose approximately 1% of gray matter volume across the transition to fatherhood, mostly in th…" 01:43 Fathers, by contrast, lose approximately 1% and the changes are confined primarily to the cortex, which governs executive functioning and reasoning. Crucially, Saxbe's lab found that paternal brain change is entirely tied to parenting behaviour: dads who felt more bonded prenatally, who took more time off after birth, who spent more daily time with their babies in the first months, and who reported greater pleasure in parenting showed the biggest brain changes. The implication is radical — simply being a biological father is not sufficient to rewire the paternal brain.
Dads who are hands-on lose about 1% of gray matter volume — mostly in the cortex — a change entirely driven by parenting time, not the mere fact of having a child. Moms lose 2.5% across the whole brain because pregnancy already primes them; dads start in the middle and the dial only moves if they engage.
New mothers lose about 2.5% of gray matter volume, affecting both the cortex and subcortex including the amygdala and reward circuitry — a larger and more widespread change than in dads.
Hands-on fathers lose approximately 1% of gray matter volume across the transition to fatherhood, mostly in the cortex — tied directly to parenting time and investment.
Chapter 2 · 02:18
Darby Saxbe frames the modern father's transformation with historical sweep. By some estimates, dads today spend three to four times more daily time parenting than their 1950s counterparts, with millennial dads at record levels and Gen Z dads pushing higher still — a shift accelerated by the pandemic's forced co-parenting experiment. [1] — Darby Saxbe "Dads' parenting time tripled or quadrupled: By some estimates, dads' daily parenting time has tripled or quadrupled compared to fathers in …" 02:23 To explain why paternal roles are so culturally variable, Saxbe introduces two contrasting African hunter-gatherer societies. The Aka of the Congo practice cooperative net hunting as couples, which makes strict role specialisation economically illogical — fathers spend extensive time within arm's reach of infants as a result. Just one day's drive away, the Kipsigis prohibit fathers from even picking up babies in their first year, believing a father's masculinity would compromise an infant's development. These examples make the point that there is no universal model of fatherhood — roles track closely with how a society generates its resources.
By some estimates, dads' daily parenting time has tripled or quadrupled compared to fathers in the 1950s and 60s, with millennial and Gen Z dads spending more time with kids than any previous generation.
In the Aka of the Congo, fathers spend extensive time within arm's reach of infants — because cooperative net hunting means there's no economic reason to specialize parenting roles. One day's drive away, Kipsigis fathers are prohibited from even picking up babies under one year old, because their riskier slash-and-burn economy demands strict role separation.
The Aka people of the Congo, a hunter-gatherer society, have fathers who spend extensive time within arm's reach of infants and are heavily involved in caregiving — reflecting the egalitarian, cooperative foraging model.
Chapter 3 · 08:18
Long before the baby arrives, the transition to fatherhood is already underway. Saxbe describes a cluster of changes in expectant fathers: hormone shifts, heightened anxiety, couple relationship strain, and sleep disruption that begins during pregnancy itself. Her neuroimaging study began mid-pregnancy, which she acknowledges may mean some brain changes were already underway — a limitation she would correct with earlier scans given more funding. The conversation turns to an arresting finding from her own lab: couples who engaged in more negative conflict during pregnancy experienced more medically complex and risky births, with both partners rating the birth as more stressful. [1] The mechanism, Saxbe explains, is physiological — stress and tension physically impair the relaxation required for effective labour, making emotional relationship health a literal obstetric variable.
Darby Saxbe's lab found that couples who fought more negatively during pregnancy experienced more medically complex and risky births, and both partners rated the birth as more stressful.
Chapter 6 · 15:17
Saxbe is unambiguous that having a baby reliably reduces relationship satisfaction — not because love disappears, but because the practical demands of new parenthood are genuinely brutal. She frames it memorably: she and her husband went from 'good time pals' to running a small business with a very disappointed customer who cries around the clock. [1] — Darby Saxbe "I used to joke that my husband and I went from good time pals to we're suddenly operating a small business with a very disappointed custome…" 16:13 She advises couples to prioritise learning to communicate effectively, especially around birth preparation — men rarely hear birth stories or see realistic birth portrayals, leaving them woefully unprepared for what labour actually looks like. The segment ends with a pointed warning: if you think having a baby will fix your relationship, you are gravely mistaken.
Chapter 7 · 17:56
The central mechanism of dad brain is one of the episode's most striking insights: biology requires behaviour. Mothers arrive at birth with their caregiving dial already turned all the way up — incubating a pregnancy costs thousands of calories and hard-wires the investment. Fathers' dials sit in the middle by default, available to rise or fall based on local demands. Saxbe introduces the concept of facultative adaptation to describe this: a biological capacity that only comes online when activated by the environment. [1] — Darby Saxbe "Mother's caregiving drive is turned all the way up at birth — incubating a pregnancy costs thousands of calories and locks in that investme…" 18:06 She draws on paternity uncertainty as an evolutionary explanation for fathers' more conditional attachment — uniquely among primates, humans conceal ovulation, incentivising men to pair bond and invest across multiple visits rather than helicopter in for a single encounter. The stability of the relationship with the mother, Saxbe adds, further modulates a father's predilection to caregive.
Mother's caregiving drive is turned all the way up at birth — incubating a pregnancy costs thousands of calories and locks in that investment. Fathers' dial sits in the middle by default, ready to rise or fall based on culture, relationship stability, and hands-on practice. This is facultative adaptation: biology that comes online when needed.
The Westermarck effect shows that witnessing parental care of an infant between ages 1 and 10 hard-wires a sexual aversion to that person. It explains the failure of sim pua marriages in parts of Asia — and by analogy, why paternal bonding is built through caregiving behavior rather than genetic fact.
Chapter 8 · 24:19
The trade-offs of parenthood extend into a surprising long-term benefit: having children appears to be neuroprotective. Saxbe cites UK Biobank data from middle-aged and older adults showing that people who have had more children have better cognitive functioning and brains that machine-learning algorithms rate as chronologically younger — with the effect plateauing at around 3 children. [1] — Darby Saxbe "More kids = younger-looking brain: UK Biobank data shows that having more children (up to about 3) is associated with better cognitive func…" 28:41 The finding holds for both mothers and fathers, which Saxbe takes as evidence that the mechanism isn't pregnancy hormones, breastfeeding, or birth experience — it's social integration. Being closely and durably connected to other people is one of the strongest predictors of brain health, and children are an unusually powerful forcing function for that connection. The conversation briefly explores whether intense friendship or pet ownership might replicate the effect, with Saxbe allowing that deep empathetic caregiving of any vulnerable creature could potentially deliver similar brain benefits.
The brain changes in new dads happen almost entirely in the mentalizing network — the seat of empathy and mind-reading. It grows because caring for a non-verbal infant is a daily workout in reading emotions and solving problems. Simply being a biological father without hands-on care produces almost none of this change.
UK Biobank data from thousands of middle-aged and older adults shows that having children is associated with better cognitive functioning and brains that AI algorithms assess as younger. The effect plateaus around 3 kids. The likely mechanism isn't hormones — it's the social integration that parenting forces on you.
UK Biobank data shows that having more children (up to about 3) is associated with better cognitive functioning and machine-learning-assessed younger brain age in middle and older age.
The neuroprotective benefit of parenthood on brain age tops off at around 3 children, after which there is no additional cognitive benefit from having more.
Chapter 9 · 31:31
A short detour into cultural testimony: Chris Williamson plays a clip of actor Bob Odenkirk articulating what many new fathers feel but struggle to express. [1] — Bob Odenkirk "I didn't have to ask myself, what am I doing here? How can I be meaningful today? I didn't have to ask that question because the fucking an…" 32:48 Odenkirk describes being deeply jealous of parents with young children at home, because those years provided him with total clarity of purpose — no existential questions about meaning or contribution, just the concrete daily work of getting kids to school and having a laugh with them. Darby Saxbe connects this to research showing that sense of meaning, coherence, and connectedness are among the most powerful drivers of psychological wellbeing, and that fatherhood is one of the most reliable delivery mechanisms for all three.
Bob Odenkirk described fatherhood as the thing that ended his existential questioning. When your kids are growing up, you don't have to ask what you're here for — the answer is picking up everything between here and the door and making sure they get to school. The meaning isn't found, it's assigned.
Chapter 10 · 33:48
The 'deadbeat dad' narrative is partly true and largely oversimplified. Saxbe charts the data: in 1960, 88% of American kids lived with a father at home; that fell to a nadir of 67% in 2005 before rebounding to around 76% today — a U-shaped trend that the binary absent/present framing entirely misses. [1] — Darby Saxbe "Father presence rebounded to 76%: Father presence in US homes dropped from 88% in 1960 to 67% in 2005, but has since rebounded to about 76%…" 33:51 Many non-residential fathers are deeply involved in caregiving; the real variable is the degree of engagement, not a simple presence or absence. Saxbe makes the point personal, describing how her own parents' divorce led to her father transitioning from a relatively hands-off caregiver to a fully primary parent on alternating weeks. She closes the segment with the story of a man who spent 3 years in jail during his son's early childhood, reconnected through parenting classes, and now directs a Project Fatherhood programme at Homeboy Industries in LA — a testament to the dial's ability to be turned back up at any point.
Father absence peaked in 2005 when only 67% of US kids lived with a dad — down from 88% in 1960. But that number has since rebounded to 76%. The real picture is more nuanced: many non-residential fathers are deeply involved, and the binary of absent vs. present misses the many shades of paternal engagement.
Father presence in US homes dropped from 88% in 1960 to 67% in 2005, but has since rebounded to about 76% of children living with a father figure at home today.
Chapter 11 · 38:50
The hormonal dimension of fatherhood is as well-documented as the neurological one, and Saxbe walks through it with the challenge hypothesis as the organising framework. [1] — Darby Saxbe "The challenge hypothesis explains that testosterone rises during mating competition and then adaptively falls when the strategy shifts from…" 39:38 Testosterone rises during mate competition — maximising opportunities to reproduce — and then adaptively falls once mating is accomplished and the strategy shifts from quantity to quality of offspring. The pattern holds across birds, rodents, primates, and humans. In new fathers specifically, the testosterone drop is linked to caregiving behaviour, not simply to the existence of a baby. The downstream effects are broadly health-protective: less risky driving, fewer fights, lower substance use, more attention to health checkups, greater investment in the pair bond. Saxbe and Chris discuss the irony of men who supplement testosterone in an attempt to signal masculinity, potentially suppressing the very adaptive shift that makes them effective fathers — with anecdotal reports from mothers suggesting the connection is real.
The challenge hypothesis explains that testosterone rises during mating competition and then adaptively falls when the strategy shifts from maximizing babies to maximizing any given baby's survival. It plays out in birds, primates, rodents, and humans alike — fatherhood isn't a hormonal failure, it's a hormonal success.
When men become engaged fathers, testosterone naturally drops — and that drop is adaptive. It reduces aggression, increases pair bonding, and promotes nurturing. Men who take exogenous testosterone may be overriding that system, and anecdotal reports from mothers suggest it shows up as reduced patience with their babies.
Darby Saxbe warned that men taking testosterone supplementation while becoming fathers risk suppressing the natural hormonal adaptation that promotes patience and caregiving behavior.
Chapter 12 · 46:44
The testosterone conversation reaches its philosophical core: what is masculinity actually for? Saxbe's answer is unambiguous — not a hormone level, but a social role. [1] — Darby Saxbe "I would argue that being a good dad is one of the most manly things you can do. You're literally rearing the next generation. You're guidin…" 47:35 Being a good dad means guiding, protecting, inspiring, and teaching the next generation; that is, she argues, what masculine capacity is evolutionarily designed for. Maintaining artificially high testosterone while suppressing the natural adaptation to fatherhood is, as Chris Williamson puts it, a 'horrendous own goal' that risks ending your lineage in the name of signalling the very thing it destroys. The conversation broadens to the parallel pressure on mothers — the 'bounce back after baby' culture that treats parenthood as an inconvenience to be reversed rather than a transformation to be embraced — and Saxbe's view that contemporary society catastrophically under-values caregiving as a public good.
Chapter 13 · 50:25
Does the neurological transformation of parenthood reset and recur with each new child? A Dutch study of second-time mothers provides a first answer: yes, but differently. [1] — Darby Saxbe "Brain change is U-shaped with more kids: Research from the Netherlands shows that maternal brain gray matter shrinks again with a second ch…" 51:30 The brain shrinks again, but in regions associated with managing multiple simultaneous inputs and task-switching rather than the same areas as the first time — precisely the cognitive skills needed to parent more than one child. Saxbe describes this as a U-shaped pattern overall, with volume loss followed by partial recovery and then another targeted loss. Chris poses the natural question about twins and triplets, which Saxbe finds genuinely fascinating: twin parents likely get a double-dose of parenting neurochemistry and may speedrun the second-child brain adaptation from birth, while also forcing greater paternal involvement simply out of necessity.
Research from the Netherlands shows that maternal brain gray matter shrinks again with a second child but in different regions, suggesting brain change is U-shaped — volume is lost then partly regained.
Chapter 14 · 53:19
In a paper her lab literally completed over the previous weekend, Saxbe reveals a striking and somewhat uncomfortable finding: the daughter effect runs in an unexpected direction. [1] — Darby Saxbe "Dads with daughters: more T drop, more stress: Darby Saxbe's lab found that new fathers of daughters show a larger drop in testosterone, sp…" 53:31 Fathers of daughters show a larger testosterone drop, spend less time caring for babies, and report more parenting stress and worse bonding in the first six months — compared to fathers of sons. Saxbe's hypothesis, which Chris Williamson arrives at independently, is that dads default to proprioceptive, rough-and-tumble, physically activating play styles that feel natural and intuitive with baby boys but less so with baby girls. Parental cognitions about children's character are also shaped by known sex before birth — girls are described as delicate and sweet, boys as rambunctious and tough — which may set up different default interaction patterns from day one. An Emory University study adds neurological detail: fathers' brains show differential responses to daughters' happy faces versus sons' distressed expressions.
Darby Saxbe's lab found that fathers of daughters show a bigger testosterone drop, spend less time with their babies, and report more parenting stress and worse bonding — compared to fathers of sons. The likely driver is that dads default to active, rough-and-tumble play styles that feel more natural with boys, leaving them less prepared for daughters.
Darby Saxbe's lab found that new fathers of daughters show a larger drop in testosterone, spend less time caring for babies, and report more parenting stress and worse bonding than fathers of sons.
Chapter 15 · 1:00:48
Saxbe's own graduate research offers a window into the physiological mechanics of modern domestic life. Following dual-income couples for a week across their LA homes, she found that housework time in the evenings correlates with less cortisol drop at bedtime — a disruption of the normal diurnal rhythm that governs stress recovery. [1] — Darby Saxbe "Housework impairs cortisol recovery: More time spent on housework in the evenings was associated with less cortisol drop at bedtime, sugges…" 1:00:52 Interestingly, the cortisol data also broke along gender lines: moms' recovery benefited when dads did more housework, while dads' recovery benefited when they had more leisure time. The follow-on finding is stress contagion — cohabitating couples have measurably linked cortisol levels, and when relationship quality is poor, that linkage tightens in a destructive direction. Partners in high-conflict relationships amplify each other's stress rather than buffering it; the solution, she argues, is teaching couples to fight in ways that de-escalate rather than escalate.
More time spent on housework in the evenings was associated with less cortisol drop at bedtime, suggesting housework disrupts the body's natural stress recovery cycle.
Cohabitating couples have measurably linked cortisol levels — when one partner is stressed, the other's cortisol rises too. Relationship conflict tightens that link, amplifying stress rather than buffering it. The fix isn't chemistry — it's learning to fight in ways that calm each other down rather than escalating.
About 10% of new fathers experience depressive symptoms in the perinatal period — roughly twice the general population rate. The risk factors overlap heavily with mothers: disrupted sleep, relationship conflict, identity crisis, hormonal changes. Yet men are never routinely screened, and the cultural gatekeeping around the term 'postpartum' is leaving depressed dads invisible.
Approximately 10% of new fathers experience depressive symptoms during the perinatal period, roughly twice the general population rate, yet it goes largely unrecognized and unscreened.
Postpartum depression affects approximately 19–21% of new mothers, roughly double the rate in new fathers, which tracks with women having twice the baseline rate of anxiety and depression in the general population.
Chapter 16 · 1:03:43
The episode's most contentious and socially urgent segment. Saxbe confirms that depression in new fathers runs at roughly twice the general population rate — about 10% — and shares all the same risk factors as maternal postpartum depression: sleep deprivation, relationship conflict, identity disruption, hormonal and neurological upheaval. [1] — Darby Saxbe "About 10% of new fathers experience depressive symptoms in the perinatal period — roughly twice the general population rate. The risk facto…" 1:02:20 She prefers the term 'perinatal depression' as gender-neutral but acknowledges the cultural minefield. Chris plays a TikTok video in which a British father describes struggling to bond with his daughter and eventually being diagnosed with postnatal depression — followed by a stream of dismissive, gatekeeping comments from women insisting this isn't real or isn't theirs. The exchange triggers one of the episode's sharpest exchanges: Chris argues that denying men's postpartum depression harms not just fathers but mothers and children directly, since the best predictor of maternal mental health is the support she receives from her partner. Saxbe connects the dots: you cannot demand full paternal involvement and simultaneously deny that involvement has mental health consequences.
The best predictor of a mother's postpartum mental health is the support she gets from her partner. When dads are depressed, moms are more likely to be depressed too — and vice versa. Treating paternal postpartum as a zero-sum resource competition ignores the fact that helping fathers directly helps mothers and babies.
A successful founder at a business networking event put his hand up not to ask about the IRS or offshore accounts, but to admit he was 6 months into his partner's pregnancy and felt nothing — and was terrified he'd be a bad dad. The room of deca-millionaires immediately erupted with recognition. Other dads had all been there.
Pregnancy physically transforms a woman into a mother through hormones, brain changes, and energetic investment. For fathers, those same transformations are available but conditional on caregiving behavior. The lack of a baby bump means the lack of a biological on-ramp — and the guilt and shame that can come from not yet feeling it.
Humans evolved as cooperative breeders — new mothers were embedded in kin networks that shared care. In contemporary society, new parents are isolated, under-supported, and pressured to return to productivity quickly. The result is an evolutionary mismatch that likely explains the high rates of postpartum depression we see today.
Chapter 18 · 1:18:55
The practical intervention session of the episode. Saxbe explains that postpartum depression is correlated within couples — depressed dads make depressed moms more likely, and vice versa — but a well partner is also a powerful protective buffer. [1] — Darby Saxbe "A Swedish paternity leave reform created a natural experiment: babies born right after expanded paternity leave was introduced had mothers …" 1:21:30 The most evidence-backed interventions centre on social integration: proactively mapping who can help with what, overcoming the cultural conditioning toward self-reliance, and leaning into community. Her lab leads psychoeducation workshops with a hospital system serving low-income new parents, walking them through social support mapping before the baby arrives. The Swedish paternity leave reform provides a rare natural experiment: babies born right after expanded paternity access was introduced had mothers who filled significantly fewer anti-anxiety prescriptions. The single clearest policy lever for maternal mental health, Saxbe argues, is giving fathers the time and permission to be present.
A Swedish paternity leave reform created a natural experiment: babies born right after expanded paternity leave was introduced had mothers who filled fewer anti-anxiety prescriptions. Darby Saxbe's own lab found the same pattern — when dads get paid paternity leave, moms are statistically less likely to get depressed after birth.
A Swedish paternity leave reform study found that babies born just after the policy took effect had mothers who filled fewer anti-anxiety medication prescriptions — showing a population-level mental health benefit for moms when dads get more leave.
The most damaging advice new dads receive is that they're biologically useless in early infancy and should step back. This myth drives fathers away from precisely the caregiving behavior that builds their brains, bonds them to their children, and protects mothers' mental health. Richard Reeves argues paternity leave should be available up to a child's 14th birthday.
No indexed bits in this chapter.
About 10% of new fathers experience depressive symptoms in the perinatal period — roughly twice the general population rate. The risk factors overlap heavily with mothers: disrupted sleep, relationship conflict, identity crisis, hormonal changes. Yet men are never routinely screened, and the cultural gatekeeping around the term 'postpartum' is leaving depressed dads invisible.
When men become engaged fathers, testosterone naturally drops — and that drop is adaptive. It reduces aggression, increases pair bonding, and promotes nurturing. Men who take exogenous testosterone may be overriding that system, and anecdotal reports from mothers suggest it shows up as reduced patience with their babies.
This episode
Factual claims made this episode, and whether a source was named.
New fathers lose approximately 1% of gray matter volume across the transition to fatherhood, with changes concentrated in the cortex.
New mothers lose approximately 2.5% of gray matter volume across the transition to first-time motherhood, affecting both cortex and subcortical structures.
Dads' daily parenting time has tripled or quadrupled compared to fathers in the 1950s and 60s.
Millennial dads are spending more time with their children than any other generation of US fathers, with Gen Z dads spending even more.
Humans spent approximately 95% of their history as hunter-gatherers.
Father presence in US homes dropped from 88% in 1960 to 67% in 2005, and has since rebounded to approximately 76%.
UK Biobank data shows that having more children (up to about 3) is associated with better cognitive functioning and younger-appearing brains in middle and older age.
Couples who fought more negatively during pregnancy experienced more medically complex births and rated the birth as more stressful.
The prevalence of depression in new dads is approximately twice that of the general population, affecting about 10% of new fathers.
Postpartum depression affects approximately 19–21% of new mothers.
Women have approximately twice the baseline rate of anxiety and depression as men in the general population.
A Swedish paternity leave reform led to measurably fewer anti-anxiety medication prescriptions among new mothers at a population level.
Darby Saxbe's lab found that when dads get access to paid paternity leave, moms are less likely to be depressed after birth.
Cortisol follows a diurnal rhythm that should peak in the morning and hit a low nadir at bedtime; more evening housework is associated with less of this cortisol drop.
Fathers of daughters show a larger drop in testosterone, spend less time caring for babies, and report more parenting stress and worse bonding than fathers of sons.
An Emory University study found that fathers' brains show different responses to happy facial expressions from daughters versus distressed expressions from sons.
This episode
Actor whose clip about fatherhood providing unambiguous daily purpose was played and discussed as a powerful illustration of the meaning that fatherhood gives men.
Author and healthy-masculinity advocate cited for his argument that paternity leave should be available until a child's 14th or 18th birthday.
A hunter-gatherer society in the Congo used as the primary model of highly involved paternal caregiving, where fathers remain within arm's reach of infants.
An African society used to contrast the Aka, where cultural prohibitions prevent fathers from picking up babies in their first year of life.
Large UK brain-scan repository cited as the source of evidence that parenthood is neuroprotective and associated with younger-appearing brains.
Sponsor offering comprehensive lab testing including full hormone panels for $365 per year.
LA-based gang intervention organisation cited as employing a formerly incarcerated father who credits his bond with his son as his life-saving turning point.
Supplements brand sponsor whose Fiber Plus product is promoted in the episode.
E-commerce platform sponsor powering 10% of US e-commerce companies including Gymshark, Skims, and the host's own Neutonic brand.
Darby Saxbe's academic home institution, where her lab has conducted over a decade of research on new fathers' brains and hormones.
Atlanta university where a study found different paternal brain responses to happy versus distressed facial expressions in daughters versus sons.
Electrolyte drink mix sponsor promoted for hydration, performance, and daily health.
Country where a paternity leave reform natural experiment showed that expanded paternity access led to lower maternal anti-anxiety medication prescriptions.
Home of the Aka people, the cooperative-foraging hunter-gatherer society used as an example of highly involved paternal caregiving.
Referenced as the home of startup entrepreneurs who, despite business confidence, privately admit to deep uncertainty and fear about their competence as new fathers.
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