Chapter 10: The Biology-Culture Feedback Loop — How Nature and Nurture Co-construct Attraction

Opening: Nadia's Notebook

Nadia Hadid keeps a journal. Not the careful, curated kind she posts online, but a private document she types late at night when her roommate is asleep — a place where she tries to think through things that feel too tangled for conversation.

One entry, written the night after the class session on hormones and attraction, reads like this:

I have been trying to figure out what it means that I am attracted to women and to men. My family has never said out loud that this would be a problem, but I can feel the edges of it — the way my mom says "when you get married" and always means a husband, the way my aunties joke about which boys in Dearborn would be suitable. I grew up watching that particular kind of love as the default, the horizon, the only map of the future I was given. And I'm attracted to men too. So how much of that — really — is just what I was taught to see? How much of my attraction to men is genuine, rooted in my body, and how much is the grooves worn into me by a thousand Hallmark movie couples and family wedding videos and cultural expectation? And how do I even tell the difference? Do I need to?

She closes the document and doesn't share it with Sam or Jordan. Not yet.

There is another entry, a week later, written after she looked up the research and read further than the assigned chapters:

I keep going back to this idea that desire is supposed to be spontaneous — that if you have to think about it, maybe it isn't real. My attraction to women has never felt spontaneous in that way. It always comes with this secondary process, this checking myself: is this real? is this just curiosity? is this about rebellion? But my attraction to men is more automatic. More quiet. And now I don't know if that means it's more "natural" — or if it just means it's had decades of reinforcement and so it comes without the meta-commentary. Like — maybe desire always has a thought process attached to it, but only the desires that conflict with your cultural script make the thought process visible.

This is a sophisticated observation, and it goes to the heart of one of the most difficult problems in the science of attraction. How do we study the spontaneity and automaticity of desire without being deceived by the fact that well-practiced responses always feel more natural than conscious ones? And how does a person — any person — distinguish between the desires that emerged from somewhere genuinely internal and those that were constructed by a world working hard to ensure they would feel that way?

What Nadia is grappling with, alone in the dark with her laptop, is one of the oldest and most contentious questions in the scientific study of attraction: how much of what we desire is the expression of something deep and biological, and how much is learned — written in us by experience, culture, and social expectation? It is a question that touches everything: the politics of sexual orientation, the ethics of desire, the nature of agency, and the meaning of "authentic" feeling.

This chapter argues that the question itself may be the problem. The nature-versus-nurture framing has done enormous damage — not just to our scientific understanding, but to real people trying to understand their own inner lives. What the evidence actually shows is something more interesting, more complicated, and ultimately more human: biology and culture do not compete to produce attraction. They co-construct it, continuously, throughout a lifetime. They are a feedback loop, not a tug of war.

Before we build the full argument, it is worth pausing to note why the false dichotomy is so durable. It persists not because scientists are foolish, but because it maps onto something psychologically real: the experience of desire as sometimes feeling alien and involuntary ("this happened to me") and sometimes feeling culturally legible and expected ("of course I felt this way"). The dichotomy maps onto that felt distinction — nature for the involuntary parts, nurture for the expected ones. The problem is that this phenomenological difference does not track anything real about the underlying mechanisms. Desire can feel automatic and irresistible precisely because cultural reinforcement has been thorough and early enough to make it unconscious. And desire can feel strange and unexpected precisely because it violates cultural scripts, not because it came from some deeper biological layer. The nature-nurture binary confuses the subjective experience of desire with its causal history.

10.1 The False Dichotomy and Why It Persists

When people ask whether attraction is "nature" or "nurture," they are usually asking a question that cannot be answered — because the two categories do not divide cleanly in the first place.

The nature-versus-nurture framing imagines two separate forces acting on a passive subject: genes on one side pulling us toward certain attractions, culture on the other side molding us into different ones. The more sophisticated version — still wrong — pictures biology as the deep layer, the substrate beneath culture's surface coating. "Nature loads the gun; nurture pulls the trigger," the saying goes. This version is cleaner and feels more scientific than the crude either/or, but it still preserves the fundamental error: it treats biology and culture as separable, sequential, and fundamentally distinct.

They are not. Here is why.

Genes require environments to express. A gene is not a blueprint; it is a recipe that can be followed in many different ways depending on what ingredients are available. The same genotype can produce dramatically different phenotypes depending on developmental environment. Genes for height, for example, have a strong heritable component — but height itself has increased by several inches across multiple generations in many countries, not because the genes changed, but because nutrition, disease burden, and early-life conditions changed. No one says this means height is "really" cultural; it means that even strongly heritable traits are environmentally modulated.

Environments change gene expression. This is the central finding of epigenetics — a field that studies heritable changes in gene activity that do not involve changes to the DNA sequence itself. Methylation patterns, histone modifications, and other mechanisms allow life experience to literally alter which genes are expressed and how strongly. Early-life stress, for example, modifies the expression of cortisol-receptor genes in ways that affect stress reactivity for years — possibly decades — afterward. The environment does not merely operate on a biological base; it becomes part of the biological base.

Development is a process, not a product. Human beings are not born and then socialized. We are socialized from the moment of birth — from the way our parents hold us and talk to us and what they show us as beautiful or frightening or desirable. Our neural architecture is shaped by this experience in ways that are physical, literal, measurable. The brain that emerges from childhood is not the "natural" brain with a cultural overlay; it is a brain that has been built, jointly, by genetic inheritance and lived experience working simultaneously.

None of this means that biology is irrelevant or that everything is socially constructed. It means that the categories themselves are less stable than we want them to be. Developmental biologist Anne Fausto-Sterling has argued for decades that bodies are not biological facts that then get gender imposed on them — bodies and gender are co-produced from the beginning of life. The same logic applies to desire.

One further point deserves emphasis: the nature-nurture dichotomy also misrepresents what "nature" means in evolutionary terms. Evolution does not produce fixed, culture-independent programs. It produces organisms with flexible systems for responding to environmental cues — because in a variable, unpredictable world, flexibility is generally more adaptive than rigidity. The idea that our "natural" attractions are somehow prior to or independent of the social world we developed in misunderstands how evolved systems work. Natural selection shaped human beings to be responsive to their social environment, to learn from it, to incorporate its signals into their developing psychology. Our capacity to be shaped by culture is itself a product of our nature. When we understand this, the question "is it nature or nurture?" starts to dissolve — not because the answer is "both," but because the question assumes a distinction the biology itself does not honor.

⚖️ Debate Point

The nature-versus-nurture debate has enormous political stakes. Conservative arguments have sometimes claimed that attraction is "natural" to enforce heterosexual norms; progressive arguments have sometimes countered by emphasizing social construction. Both moves can distort the science for political purposes. The honest position is that "natural" does not mean inevitable, fixed, or morally significant — and "socially constructed" does not mean arbitrary or unreal. A socially constructed desire is still a real desire. Understanding how it was constructed does not make it less yours. Moreover, the appeal to "nature" has a troubling historical track record: it has been used to justify slavery (enslaved people were "naturally" suited to servitude), to oppose interracial marriage (couples were "naturally" drawn to their own kind), and to pathologize homosexuality (heterosexuality was the "natural" expression of human sexuality). None of these appeals to nature reflected the science of the time; all of them reflected the ideology. This history should make us permanently alert to the gap between "X is natural" and "X is morally correct or inevitable."

10.2 Gene-Environment Interaction: What Epigenetics Actually Tells Us

Epigenetics has become one of the most overhyped and most misunderstood fields in contemporary science. Popular accounts swing between two errors: dismissing it as irrelevant to behavior, or treating it as proof that "your environment is your destiny." The actual findings are more nuanced and, in many ways, more illuminating.

The core finding that matters for attraction research is this: the same genetic predispositions can produce very different behavioral outcomes depending on the developmental environment, and those differences can persist into adulthood through mechanisms that are biological, not merely psychological.

Consider research on the heritability of sexual orientation. Twin studies consistently find that identical twins show higher concordance rates for sexual orientation than fraternal twins, suggesting a genetic component. But the concordance rate for identical twins is not 100 percent — if it were, sexual orientation would be entirely genetic. The fact that it is significantly less than 100 percent in virtually every study tells us that genes are not destiny. Something else is contributing. What?

Several researchers have proposed epigenetic mechanisms. A 2015 study by Ngun and colleagues (since disputed and partially retracted — an important methodological reminder) proposed that epigenetic marks in certain regions of the genome could predict sexual orientation. The specific claims did not replicate cleanly, but the theoretical framework they invoked is sound: gene expression, not just gene sequence, varies in ways that are responsive to developmental environment, and this could plausibly contribute to variation in sexual orientation.

More robust findings come from other domains. Research on the DRD4 dopamine receptor gene shows that variants associated with novelty-seeking behavior — potentially relevant to desire and romantic exploration — produce different behavioral outcomes depending on rearing environment. In warm, supportive environments, the "risk" variant may confer benefits (openness, curiosity, engagement); in harsh environments, the same variant may be associated with more problematic outcomes. The gene does not predetermine behavior; it interacts with context.

Another domain of epigenetic research relevant to attraction involves prenatal hormonal exposure. The organizational hypothesis in sex research holds that prenatal exposure to androgens (including testosterone) during sensitive developmental periods shapes the organization of the brain in ways that influence later behavior, including sexual behavior. Evidence for this comes from natural experiments — notably congenital adrenal hyperplasia (CAH), a condition that results in elevated prenatal androgen exposure. Studies of women with CAH generally find elevated rates of same-sex attraction, greater gender nonconformity, and other shifts in the direction of typically male-typed psychology. This is real biological influence on attraction — but it is still an example of gene-environment interaction: the gene (in this case, the enzyme-coding gene affected by CAH) produces its effect through a hormonal mechanism that is itself embedded in a developmental process and expressed in a cultural context.

The key methodological issue with all this research is the difficulty of establishing what the baseline "no biological influence" condition would even look like. Because every human being develops in an environment — physical, social, hormonal — there is no clean control case. Researchers are always comparing one developmental environment to another, not biology to culture in isolation. This does not make the research uninformative, but it does mean that findings about "biological influences" on attraction always carry the asterisk: "influence in these developmental conditions, in these cultural contexts, measured with these instruments."

💡 Key Insight: The Co-Evolutionary Model

Epigenetics offers one mechanism for how nature and culture interact, but it describes change within a single organism's lifetime. The co-evolutionary model goes further: it proposes that culture and biology evolve together over longer timescales, each shaping the conditions under which the other changes. Human beings have been shaping their own evolutionary environment through cultural practices for tens of thousands of years — and that cultural environment has, in turn, shaped the selection pressures acting on human biology. This is not metaphor. It is a well-supported framework in evolutionary biology called niche construction theory. The lactase persistence example is instructive: the cultural practice of cattle herding created selection pressure for the genetic mutation that allows adults to digest milk — culture produced a biological change. Analogous processes, over much longer timescales, may explain aspects of human sexual and social psychology that look like "pure biology" but reflect the accumulated pressure of cultural practice.

10.3 Developmental Plasticity: The Wiring Happens Early (But Not Permanently)

One of the most important and least comfortable findings in attraction research is that the groundwork for adult desire is laid surprisingly early. Children are not sexually attracted to anyone — that develops at puberty — but the basic templates of what feels safe, intimate, and interesting in another person begin forming from the first months of life.

Attachment theory, which we will explore in depth in Chapter 11, documents how early caregiving relationships create working models of intimacy that persist into adult romantic life. A child who experiences love as reliable and warm develops different expectations and relational tendencies than a child who experiences it as anxious, inconsistent, or absent. These differences are measurable in adult attachment styles, in relationship satisfaction, and in the specific qualities people seek in partners.

But developmental plasticity — the brain's capacity to be shaped by experience — cuts in multiple directions. Yes, early experience leaves marks. But the brain remains plastic far longer than was once believed. Adolescence involves a massive second wave of synaptic pruning and reorganization. Young adulthood is a period of significant identity and relationship development. Even in midlife, the brain retains more capacity for change than older models assumed.

One of the most important sites of developmental plasticity in the context of attraction is adolescence itself — the period during which sexual desire first emerges in full form. The onset of puberty brings not just hormonal changes but a reorganization of the social brain. Adolescents become dramatically more sensitive to peer evaluation, to social status signals, to information about who is desirable and why. This is a critical period not just for physical maturation but for the social learning of desire — for absorbing, from one's specific peer culture, what counts as attractive, what counts as an eligible partner, and what one's own desirability looks like in that social field.

Research on adolescent sexual identity development documents that the period between first same-sex attraction and adult identity formation has shortened dramatically in recent decades — most likely because cultural availability of gay identities and narratives has increased. This is direct evidence that developmental plasticity interacts with cultural context: the same underlying biological predispositions express differently in different cultural environments because the developmental period in which they become organized is itself culturally saturated.

For Nadia, this means something specific. Her first awareness of attraction to women — which she can trace to a particular friendship in high school that she didn't have words for at the time — emerged in a cultural context where lesbian identity existed as a concept, where queer women had some media representation, but where her family's cultural and religious framework made the concept difficult to integrate. The developmental period in which her attraction organized itself was shaped by both of these contradictory cultural forces simultaneously. What emerged is not "her nature" untouched by culture, nor "her culture" untouched by nature — it is the specific person she became at the intersection of both.

This has important implications for thinking about desire. Early experiences with what felt desirable — gleaned from media, family models, peer culture, and formative relationships — do create grooves that influence later attraction. But those grooves are not destiny. They can be deepened by repetition, modified by reflection, and in some cases substantially revised by powerful new experiences.

This is one reason why sexuality researchers now speak of developmental plasticity in desire rather than fixed orientation determined at birth. The question is not whether early experience shapes desire (it does) but how much later experience can reshape it — and for whom, and under what conditions.

🧪 Methodology Note

Research on developmental plasticity in attraction faces a persistent challenge: retrospective bias. Most studies ask adults to recall when they first noticed certain attractions, which beliefs or norms surrounded them at the time, and how their desires have changed. Human memory for emotional and relational experience is notoriously reconstructive — we tend to remember our pasts as more coherent with our present self-understanding than they actually were. This means that people who now identify as gay may remember their childhood attractions as more clearly homosexual than they reported them at the time, and people who have experienced attraction change may narrate a story of "finally becoming myself" that imposes a particular arc on a messier reality. Longitudinal designs like Diamond's — where experiences are captured as they happen — are methodologically superior precisely because they avoid this problem, but they are expensive, time-consuming, and rarely conducted.

10.3b A Note on Sexual Orientation Research: What We Know and Don't Know

Because sexual orientation is both politically charged and scientifically contested, it deserves a brief standalone treatment before we continue.

The scientific consensus — to the extent one can be identified — holds that sexual orientation in humans is influenced by biological factors (genetic, hormonal, neurological) operating during development, but that no single "cause" has been identified and the system is clearly more complex than any single-factor account. The 2019 genome-wide association study by Ganna and colleagues, the largest genetic study of sexual behavior to date, found genetic variants associated with same-sex sexual behavior but concluded that they explained only a small fraction of the variance and that many genes of small effect were involved. Crucially, the genetic variants associated with same-sex behavior also showed associations with personality traits like openness to experience — suggesting that the genetic architecture of sexual orientation overlaps with broader systems of personality and behavioral flexibility rather than being a single discrete "gay gene."

This finding is consistent with a co-evolutionary account: sexual orientation is not a simple binary trait coded by a single genetic switch, but rather the outcome of multiple interacting biological systems (each with genetic contributions) operating in a developmental context that is itself culturally structured. The result is a distribution of human desire that is wide, complex, and considerably more varied than the simple hetero/gay binary captures.

For our purposes, the most important implication is this: any explanation of sexual orientation that stops at either "it's genetic" or "it's a choice" is inadequately describing a much more complex system. The co-evolutionary model does not resolve all uncertainties about sexual orientation — no model currently does — but it provides a more accurate framework than either extreme, and it is more consistent with the full range of what people actually report about their desires and their experiences of those desires over time.

10.4 Cultural Norms as Evolutionary Environment

One of the most elegant ideas to emerge from the interface of evolutionary biology and cultural theory is the concept of niche construction: the process by which organisms modify their own environment, which then alters the selection pressures acting on them.

Beaver dams are the classic example. Beavers build dams; dams create ponds; ponds change the ecosystem in ways that create new selection pressures on beavers themselves (different predators, different food sources, different disease risks). The beavers are not passive recipients of evolutionary pressure — they are actively modifying the conditions under which evolution occurs.

Human beings are the supreme niche constructors. We have built an astonishing variety of cultural environments — agricultural societies, industrial cities, digital networks, religious institutions, legal systems, kinship structures — each of which creates different selection pressures and different developmental contexts for desire.

Here is a concrete example. Pair-bonding norms vary significantly across human cultures. Monogamy, polygyny (one man, multiple wives), polyandry (one woman, multiple husbands), and various other arrangements appear across the anthropological record. If human sexual psychology were simply the output of fixed biological programming, we would expect far less variation. What we see instead is that human reproductive biology has a degree of inherent flexibility that allows it to be organized in multiple different ways by cultural systems — and that those cultural systems, once established, create the social environments within which children develop and form their first templates of desire.

The implication is that cultural norms do not merely constrain or express "natural" attractions. They actively participate in constructing which attractions feel natural in the first place.

A concrete and disturbing example: the history of beauty ideals in Western societies shows that what is considered maximally attractive in women has shifted substantially across historical periods — from Rubensian voluptuousness to Victorian waist constriction to the mid-twentieth-century hourglass to the 1990s heroin chic thinness to the current (contested) hourglass-with-fitness ideal. These shifts correlate with economic conditions, with the status of women in the workforce, and with the specific industries (fashion, film, advertising) that profit from shifting standards. If beauty standards were simply read off from a biological template encoding signals of fertility and health, they would be more stable. The instability is precisely what we would predict if cultural systems — including economic systems with specific interests in maintaining anxious consumption — are participating in constructing what counts as desirable.

This does not mean that beauty preferences have no biological dimensions. It means that the biological dimensions are not sufficient to explain the full pattern of what we see. And it means that when a person feels a powerful, apparently spontaneous attraction to a specific body type — one that happens to match the dominant media standard of their era — we should not automatically infer that they have simply read off their genes. They may have; they may also have internalized a cultural norm so thoroughly that it feels like nature. The two are not distinguishable from the inside.

🔵 Ethical Lens: Whose "Nature" Gets Normalized?

If cultural norms function as an evolutionary environment that shapes what feels natural to those who grow up within them, we have to ask a critical question: whose norms get to count as "nature"? Western European, heterosexual, patriarchal norms have dominated much of the psychological and evolutionary literature on attraction — and have often been presented as natural baselines against which other desires are measured as deviations, pathologies, or curiosities. This is not politically neutral science. When we say that certain attractions are "natural," we are often pointing to attractions that have been normalized by the specific cultural niche in which most of our research has been conducted. Other attractions are no less biological, no less genuine — they have simply developed in a different niche, or in tension with the dominant one.

10.5 Neuroplasticity and Learned Attraction

The brain changes with use. This is no longer a controversial claim; it is one of the most replicated findings in neuroscience. Neural pathways that are used frequently are strengthened through myelination and synaptic consolidation; pathways that go unused are pruned. This process — neuroplasticity — is the biological mechanism underlying learning of all kinds, from motor skills to language to emotional patterns.

What does neuroplasticity mean for attraction? It means that what we find attractive can be shaped — and reshaped — by experience. Not arbitrarily, not without constraint, but genuinely and measurably.

The mere exposure effect, documented by Robert Zajonc in classic social psychology research, shows that repeated exposure to a stimulus reliably increases liking for it — across cultures, across sensory modalities, and across age groups. We tend to be attracted to what is familiar. This is not just a psychological quirk; it reflects neural processes in which familiar stimuli require less effortful processing, generating a positive affective signal.

This has direct implications for attraction. People who grow up surrounded by a particular group — in terms of race, body type, class presentation, or any other dimension — tend to develop attraction patterns that include those groups more readily. This is not moral endorsement of those patterns; it is a description of a mechanism. And it is a mechanism that cuts against the idea of "natural" attraction preferences as fixed and culture-independent.

The same logic applies to media exposure. Decades of research show that consistent media representation of particular body types, racial pairings, gender dynamics, and romantic scenarios shapes the templates of desirability that audiences internalize. This is not subliminal manipulation; it is ordinary neuroplasticity operating on the raw material of cultural content. The neural architecture of attraction is being built in real time by what we encounter, what is shown to us as beautiful, what stories we are given about who belongs with whom.

There is an important racial dimension to this argument that deserves explicit attention. Research on racial preferences in dating consistently finds that White individuals receive more messages and matches across dating platforms in the United States, and that many users express explicit same-race preferences. A straightforward "biological" account would explain this in terms of in-group preferences or evolutionary psychology's documented in-group favoritism. But the pattern is more complex: the magnitude of racial preference hierarchies in dating varies across platforms (those with more diverse user bases show less extreme hierarchies), varies across cities (more diverse urban areas show flatter hierarchies), and — critically — varies across cohorts, with younger daters showing less pronounced racial hierarchies than older ones. If this were simply biological in-group preference, we would expect more stability. The pattern instead looks like a system shaped heavily by cultural familiarity and media representation: who is shown as desirable, in what contexts, for what kinds of relationships. The mere exposure effect operating on a racially stratified media system produces racially stratified attraction templates.

This is not a comfortable finding. It means that some of what people experience as genuine, spontaneous attraction — the feeling that a certain type of person is or isn't "their type" — may be partly an artifact of a racially unequal cultural environment. This does not make those preferences fake, but it does make them political — products of history and power, not just of biology and individual choice.

🔗 Connections

The mere exposure effect connects to the discussion of physical attractiveness standards in Chapter 8 — recall the cross-cultural data from the Okafor-Reyes study showing both commonalities and significant variation in beauty standards across countries. The variation makes more sense when we understand that familiarity is itself an attractiveness cue, and that what counts as familiar varies by the environment in which you grew up. Chapter 25 will take up racial preferences in dating data directly, using the Swipe Right Dataset to examine how race and attraction intersect at the level of behavior.

10.6 The Coolidge Effect and What It Tells Us About "Natural" Drives

The Coolidge effect refers to the tendency — documented across many mammalian species — for male animals to show renewed sexual interest in novel females even after satiation with a familiar partner. It is named (somewhat improbably) after U.S. President Calvin Coolidge, based on a probably apocryphal anecdote involving a chicken farm.

The Coolidge effect has been enthusiastically adopted by certain corners of evolutionary psychology and popular culture as evidence that male desire for novelty and variety is "hardwired" — a natural drive that cultural monogamy rules merely suppress. The pickup artist community has used it to argue that male infidelity is biologically inevitable; anti-feminist writers have used it to suggest that male sexual boredom in relationships is natural and therefore not a moral failing.

Let's examine what the research actually shows — and where these popular extrapolations go wrong.

First, the Coolidge effect is well-documented in non-human animals, particularly male rodents. The neural mechanisms involve dopaminergic reward circuits that respond more strongly to novel stimuli than familiar ones — the same circuits that underlie curiosity, exploration, and learning generally.

Second, the effect has been documented in humans too — though the evidence is more complex. Studies using both self-report and physiological measures show that subjective arousal can increase in response to novel sexual stimuli, for both men and women, though average effect sizes tend to be larger for men.

Third — and this is the critical point — the presence of a drive is not the same as its inevitability or its moral license. Humans have strong drives toward aggression, resource hoarding, in-group favoritism, and many other behaviors that we have collectively decided to regulate, manage, and sometimes transform through cultural practices, moral norms, and individual choice. The question for any drive is not "is it natural?" but "how do we want to live with it?"

Fourth, and perhaps most importantly, the cultural container in which novelty-seeking operates dramatically shapes how it expresses. In polyamorous communities with negotiated norms, novelty can coexist with deep commitment. In monogamous contexts with strong social reinforcement, long-term partners report sustained attraction through practices that cultivate novelty within the relationship. The "drive" does not dictate the outcome; the cultural framework within which it is expressed shapes what that drive actually does in a person's life.

⚠️ Critical Caveat

Much popular writing about the Coolidge effect and male desire for novelty relies on studies with severe methodological limitations: mostly male, mostly Western, mostly college-aged samples; heavy reliance on pornography viewing as a proxy for "natural" sexual response; and conflation of laboratory arousal with real-world relationship behavior. The gap between "college men show more arousal to novel images in a lab" and "men are biologically incapable of monogamy" is a gap that requires enormous extrapolation across contexts, species, and timescales. That gap should be filled with evidence, not just confident assertion.

10.7 Sexual Fluidity: Lisa Diamond's Contribution

In 2008, developmental psychologist Lisa Diamond published a landmark book based on ten years of longitudinal research following a diverse sample of women who identified as lesbian, bisexual, or unlabeled. The book, Sexual Fluidity: Understanding Women's Love and Desire, reported findings that both challenged mainstream assumptions about sexual orientation and were promptly misunderstood by almost everyone.

What Diamond found, in brief, was this: over the course of the ten-year study, a substantial minority of the women in her sample changed their self-identified sexual orientation — not because of social pressure or confusion, but because their actual attractions shifted. Women who had identified as lesbian reported genuine attraction to men. Women who had identified as bisexual sometimes experienced periods of predominantly same-sex or predominantly other-sex attraction. The pattern was not random — most women showed a clear central tendency in their attractions — but it was not fixed and static in the way that "sexual orientation as biological trait" models would predict.

Diamond was careful about what her findings did and did not mean. They did not mean that sexual orientation is a choice. They did not mean that orientation change therapy (conversion therapy) works or is acceptable — her data showed no evidence of willed change; the shifts she documented were spontaneous and often surprising to the women themselves. And they did not mean that sexual orientation is "merely" social or cultural.

What they did mean was that human sexual desire, at least for a significant proportion of women, shows more flexibility across time and context than the essentialist model assumes. This flexibility appears to be a real feature of human sexuality — not a sign of confusion or instability, but evidence of the kind of developmental plasticity we discussed earlier.

📊 Research Spotlight: Lisa Diamond's Longitudinal Study

Study design: 100 women recruited from LGB community events, college organizations, and friend networks in upstate New York. Interviewed at Time 1 (1995), then re-interviewed every two years through 2005. Final sample after attrition: 89 women, with complete data for most.

Key findings: - 67% of participants changed their identity label at least once over 10 years - Changes occurred in multiple directions — not just toward heterosexuality - 36% changed their "identity" while reporting stable underlying attraction patterns; 64% reported genuine shifts in attraction - Women who identified as "unlabeled" showed the most stability in attraction patterns — less constrained by identity label expectations - Romantic love and emotional intimacy predicted shifts in attraction more than sexual fantasy patterns

Limitations: Sample was drawn from LGB-identified community events and may overrepresent women already open to fluid identification. Research conducted in a specific historical moment. Not directly replicable for men (Diamond's subsequent work explores whether male desire shows less fluidity — preliminary evidence suggests it may, though this remains debated).

Methodological note: Diamond's longitudinal design is notably stronger than most cross-sectional studies of sexual orientation. The ten-year window allowed genuine change to be distinguished from measurement error or situational factors.

Diamond's own interpretation draws explicitly on the framework we have been building throughout this chapter. Sexual desire, she argues, is organized at two levels: a relatively stable dispositional orientation (toward people of the same sex, other sex, or both) and a more context-sensitive behavioral and affective system that responds to specific people, relationships, and circumstances. The first level may have stronger biological determination; the second is more malleable. Fluidity occurs primarily at the second level — not in the deep structural organization of attraction but in how that structure expresses in real relationships and real lives.

This model is well-suited to the biology-culture feedback loop we are tracing. The dispositional level may reflect stronger genetic and prenatal influences; the situational level is more continuously shaped by experience, relationship context, and cultural possibility. For Nadia, wrestling with her attractions in her private journal, this framework offers something important: her attractions are not proof that she has been confused by culture into performing a false self. They are the product of a self being built, in real time, from everything she is and everything she has lived.

10.8 Testosterone and the Direction of Causation

Few substances in the popular scientific imagination carry as much explanatory weight as testosterone. It is invoked to explain male aggression, risk-taking, dominance hierarchies, infidelity, violence, and sexual desire — often in a way that implies it is the master variable, the biological prime mover that causes all these behaviors.

The actual science is considerably more complicated, and much of what "everyone knows" about testosterone is either overstated, misunderstood, or flatly wrong.

Testosterone is a steroid hormone produced primarily in the testes and ovaries, with smaller amounts produced in the adrenal glands. It plays important roles in development — both prenatal and pubertal — and continues to influence various biological processes throughout the life course. Average testosterone levels are higher in men than in women, though the distributions overlap considerably, and testosterone levels vary dramatically across individuals, across time of day, and across life circumstances.

Here is where the science gets interesting: the relationship between testosterone and social behavior is not unidirectional. The popular model imagines testosterone as a cause — high testosterone produces dominance, aggression, and sexual drive. But the research shows that social context also causes changes in testosterone. Winning a competition raises testosterone. Losing one lowers it. The physical presence of an attractive potential partner raises testosterone — in both men and women. Being in a committed long-term relationship is associated with lower average testosterone in men. Becoming a father is associated with testosterone decline in men in many cultures, a pattern that appears to facilitate caregiving behavior.

This bidirectionality is crucial. Testosterone is not just a cause of social behavior; it is also a result of social experience. The body is continuously adjusting its hormonal state in response to the social environment, which then produces further behavioral changes, which then alter the social environment, which then changes hormone levels again. This is a feedback loop — the same structure we identified at the level of culture and biology.

🔴 Myth Busted: "Testosterone explains male desire for sex/dominance/infidelity"

This claim vastly oversimplifies a complex system. The key problems:

1. Testosterone levels within the normal range for either sex correlate poorly with sexual desire — subjective libido is influenced by many factors beyond hormone levels
2. The causal arrow runs both ways: social wins, attractive partners, and competitive contexts raise testosterone; it is not purely a cause of behavior
3. Cultural context dramatically moderates the relationship between testosterone and aggression — cultures with different honor norms show different testosterone-aggression correlations
4. Testosterone does not distinguish between sexual desire and other forms of motivated behavior — it appears to raise motivational intensity generally, not sexual desire specifically

Source: Cordelia Fine's Testosterone Rex (2017) provides a comprehensive, rigorously evidenced critique of testosterone determinism.

The work of Cordelia Fine — cognitive neuroscientist and author of Testosterone Rex and Delusions of Gender — has been particularly important in documenting how testosterone mythology gets constructed and then reproduced in popular science. Fine's argument is not that testosterone does nothing; it clearly does many things. Her argument is that the popular narrative of testosterone as a master switch that automatically produces male-typical behavior across all contexts dramatically misrepresents what the science actually shows.

For our purposes — understanding how biology and culture interact in attraction — the testosterone story is a microcosm of the broader principle. Hormones are not independent variables that cause attraction to happen in predictable ways; they are nodes in a feedback loop that includes social context, developmental history, relationship experience, and cultural environment.

One more finding deserves mention before we leave the testosterone discussion. The relationship between testosterone and competitive motivation appears to be strongly moderated by cultural context, specifically by norms around masculine honor. Studies conducted in the southern United States — a region with stronger honor culture norms than the Northeast — show that testosterone responses to insult are larger and more behaviorally consequential than comparable studies in non-honor-culture regions. The same hormonal response, in the same bodies, produces different behavioral outputs depending on the cultural meaning system in which it is embedded. This is gene-environment interaction not at the level of development but at the moment of social encounter — the culture is in the room, shaping how the biology expresses.

This finding has implications for attraction specifically. Testosterone's effects on mating-relevant behavior — mate-guarding, competitive display, risk-taking in romantic contexts — are not culture-independent. How they express depends on what cultural scripts are available for making sense of and acting on elevated motivational states. A man who feels heightened competitive arousal in the presence of an attractive person will interpret and act on that feeling differently depending on whether his cultural environment valorizes aggressive pursuit, restrained dignity, egalitarian negotiation, or some other approach to desire. The biology sets up the system; the culture provides the interface.

10.9 Nadia's Question: Are My Desires Fully My Own?

Return to Nadia's notebook. After weeks of sitting with the question — of reading the research, attending the seminar, and turning things over in conversation with Sam and Jordan — she writes a new entry:

I think I've been asking the wrong question. I keep trying to figure out which parts of my attraction are "really me" and which parts are "just my upbringing." But the more I read, the more I think that's not actually a coherent question. My upbringing is me. The grooves that got worn into my brain by watching my parents' marriage, by the movies I grew up with, by the particular way my community talks about who belongs with whom — those aren't a cage on top of my real self. They're part of how my self got built. Even my rebellion against some of those norms — my choice to acknowledge my attraction to women, which my family's expectations actively discouraged — that too is a product of a particular environment: a college campus, a women's studies class, a friend group that made certain possibilities visible.

I don't think this means my desires aren't mine. I think it means that "mine" is more complicated than I thought. My desires are mine the way my values are mine — I didn't choose them from scratch, but they're also not external constraints. They emerged from me, through a particular life. And I can reflect on them, ask questions about them, decide which ones I want to cultivate and which ones I want to interrogate. That's not nothing. That might actually be what agency looks like.

Nadia has arrived, through her own reflection, at something like the philosophical position we have been building throughout this chapter. She has moved from "nature versus nurture" to something more like "co-construction through lived experience." Her desires are both biological — involving hormonal systems, neural circuits, and genetic predispositions — and cultural — shaped by media, community, family, religion, and social norms. Neither explanation erases the other. Neither makes her desires less real or less hers.

There is something else in Nadia's journal that she doesn't have words for yet, but that we can name: she is distinguishing between desire as a state (what she feels, right now, when she encounters a person who attracts her) and desire as an identity (what kind of person she is, what category she belongs to, what her desires say about her as a whole). The state is biological in a fairly direct sense — it involves neural activation, hormonal response, affective experience. The identity is cultural through and through — it is organized by the categories her community provides, the stories available about what her desires mean, the social consequences that follow from claiming or not claiming certain identities.

This distinction — desire-as-state versus desire-as-identity — helps explain something that puzzles many people about their own experience: how it can feel both completely natural and deeply personal to experience a desire, while simultaneously feeling strange and constructed to attach a social identity to it. The desire emerges from your biology in interaction with your developmental history. The identity emerges from your culture's taxonomy of human types. These are two different things, built from different materials, with different stabilities and different degrees of choice attached to them.

For Nadia, who grew up in a community where "bisexual Lebanese-American woman" is not a readily available identity category, the gap between her desire-as-state (which she experiences clearly) and her desire-as-identity (which has no clean social container in her world) is a source of real cognitive and emotional work. This is not a sign that something is wrong with her, or that her desires are not genuine, or that her culture has constructed them artificially. It is a sign that she is a person living at the intersection of a biological desire system and a cultural identity system that are not perfectly synchronized — which is to say, she is a person. Most of us live with some version of this gap.

🔵 Ethical Lens: Desires Shaped by Oppressive Systems

Nadia's reflection lands on a relatively comfortable conclusion — her desires emerged from her experience, and she can reflect on them with some degree of agency. But her situation is complicated, and not everyone's is resolvable in the same way. Consider this harder version of the question: what if your desires were shaped significantly by systems of oppression? Research documents that people who have experienced racial fetishization — being desired specifically because of racial stereotypes rather than individual characteristics — sometimes internalize aspects of that framing in their own self-assessment of desirability. Sexual preferences that track racial hierarchies are partially produced by those hierarchies. This does not make them less real as desires, but it does complicate the claim that they are neutral expressions of individual biology. It is possible to hold both truths simultaneously: desires are genuinely yours, and some desires have histories worth examining.

10.10 Okafor-Reyes: Cross-Cultural Complexity

When Dr. Adaeze Okafor presents preliminary findings from the Global Attraction Project at a conference in year 3, she focuses on a specific puzzle in the data: the pattern of cross-cultural variation in attraction preferences is neither consistent with simple biological universalism nor consistent with pure cultural relativism.

Some dimensions of attraction show striking consistency across all 12 countries in the study: preferences for facial symmetry, for cues of health, for evidence of prosocial character in long-term partners. These patterns are weak effects — not destiny — but they appear consistently enough across dramatically different cultural contexts that a purely constructionist account has difficulty explaining them.

Other dimensions show strong cultural specificity: preferences for body weight and shape, for the significance of family approval, for the role of economic status in partner choice, for the desirability of particular personality traits. These differences are large enough that a purely biological account has even more difficulty.

And then there is a third category: patterns that are consistent on average but show high variance within cultures, with the variance appearing to track specific subgroup experiences. Same-sex attraction rates don't vary dramatically across cultures in self-report data (though reporting probably varies with social acceptability), but the degree to which same-sex attracted individuals experience their attraction as chosen, fixed, or fluid does vary with cultural context — specifically, with the degree of stigma and the availability of gay-identified communities and narratives.

For Okafor and Dr. Carlos Reyes, this third category is the most theoretically interesting. "We're not finding that biology and culture operate separately," Okafor tells her audience. "We're finding that culture affects how biological predispositions get organized, expressed, and experienced. The interaction isn't additive. It's constitutive. The culture doesn't just add a layer on top of the biology — it shapes what the biology produces."

Reyes, who has been quietly annotating his own copy of her slides, adds one comment from the audience: "And the reverse is also true. The range of cultural variation we're finding isn't infinite. The biology constrains which cultural forms are stable. It's a genuine bidirectional system."

Later, in the hallway after the talk, a graduate student asks Okafor the question that always comes: "So does this mean sexual orientation is a choice?" Okafor pauses. "It means the question is built on a false premise," she says. "A choice implies you could have done otherwise under the same circumstances. But what are 'the same circumstances'? Your circumstances include your biology, your developmental history, your cultural context, all of it. Change any of those and you might get different attractions. But that's not choice in any morally meaningful sense — that's just causation. Everything about you has causes. That doesn't mean you didn't choose anything. It means choices are embedded in causes, not free of them." The graduate student writes this down. Reyes, overhearing, nods.

The point Okafor makes here is not just philosophical. It has direct methodological implications for the Global Attraction Project. If they want to understand attraction, they cannot treat "biology" and "culture" as separate independent variables to be controlled for. They have to treat their interaction as the primary object of study — which means their research design, their analysis strategy, and their interpretation of findings all need to accommodate the possibility that biology and culture are not merely correlated but constitutively entangled. This is methodologically harder, but it is what the phenomenon actually requires.

10.11 The Co-Evolutionary Model: A Synthesis

We are now in a position to articulate the co-evolutionary model clearly, as the synthesis of everything in this chapter and, indeed, of Part II as a whole.

The co-evolutionary model holds that:

1. Human beings have evolved biological systems — hormonal, neural, genetic — that provide the raw material for sexual and romantic attraction. These systems include motivational drives, social-bonding mechanisms, pattern-recognition capacities, and emotional response networks that are relevant to desire.

2. These biological systems are not closed programs. They are open to developmental modulation. Early experience, adolescent learning, and adult relationships all leave physical traces in neural architecture. The biology of attraction is plastic, not fixed.

3. Cultural systems function as evolutionary environments. The norms, representations, institutions, and social practices that humans have built create the conditions under which human biology develops. They determine what is familiar, what is sanctioned, what is available, and what is narrated as desirable. Over long timescales, they influence selection pressures. Over individual lifespans, they shape the developmental environment in which attraction capacities are organized.

4. The influence runs both ways. Cultural norms shape what people find attractive; what people find attractive shapes cultural norms. Media representations both reflect and produce desire patterns. Institutional structures (marriage, family law, religious practice) both express and reinforce attraction templates. This is a genuine feedback loop, not a one-way causation.

5. Individual experience mediates between cultural templates and personal desire. No one is simply a product of their culture's attraction norms. Every person's developmental trajectory involves a specific, idiosyncratic combination of biological predispositions, family environments, formative relationships, and cultural exposure. This is why there is so much variation within cultural groups, and why personal reflection — like Nadia's — can identify both the cultural grooves in our desires and the places where our experience diverged from them.

6. Agency exists, but it is not unlimited. The fact that desires are co-constructed does not mean they are unchosen in any sense that matters morally. We have some capacity — through reflection, through exposure to new experiences, through therapeutic and communal work — to examine and sometimes to shift our desire patterns. This capacity is real, but it is not unlimited, and it is not evenly distributed. People whose desires were shaped by oppressive systems face different and often harder work in that reflection.

💡 Key Insight: Implications for Research

The co-evolutionary model has important implications for how we design and interpret attraction research. It means that: - Studies done exclusively in Western, educated, industrial, rich, democratic (WEIRD) societies cannot establish biological universals — they establish patterns in one particular cultural niche - Cross-cultural variation in attraction is data about the co-evolutionary system, not noise to be explained away - Longitudinal research is more valuable than cross-sectional snapshots for understanding how attraction develops and changes - We should be skeptical of any account that invokes "biology" to explain attraction patterns without specifying the developmental and cultural context in which that biology was expressed

10.12 Building Toward Part III

Part II has built a picture of human attraction grounded in biological systems — hormonal, genetic, neural, evolutionary — while consistently complicating the reductive claim that biology is destiny. We have seen how physical beauty standards vary across cultures even while showing some consistent cross-cultural features (Chapter 8). We have traced the neurochemistry of desire and pair-bonding (Chapter 9). And now, in this synthesis chapter, we have argued that none of these biological systems can be understood in isolation from the cultural environments in which they develop and express.

Part III turns inward — toward the psychological level of analysis. If Part II asked "what biological systems are involved in attraction?", Part III asks: "How do individual people, with their particular histories and psychological structures, experience and navigate desire?"

The co-evolutionary model is the bridge between these levels. Psychological structures — attachment styles, self-concept, cognitive biases, emotional regulation patterns — are themselves products of the feedback loop between biological predisposition and developmental experience. When we study attachment theory in Chapter 11, we will be asking how early relational experience, filtered through biological systems for social bonding, produces the psychological templates that shape adult desire. When we study self-esteem and desirability in Chapter 13, we will be asking how cultural messages about who is attractive become internalized as psychological beliefs about one's own worth.

The move from Part II to Part III is not a move from biology to psychology, as if these were separate levels. It is a move from the systemic to the individual — from the mechanisms that produce attraction generally to the ways that particular human beings experience, interpret, and act on their desires. Both levels require the co-evolutionary lens. A psychology that ignores biology produces just-so stories about social construction; a biology that ignores psychology produces just-so stories about evolutionary inevitability. The science of attraction needs both.

Chapter Summary

This chapter has argued that the nature-versus-nurture framing of attraction is a false dichotomy that obscures more than it reveals. In its place, we have developed a co-evolutionary model that holds that:

• Genes require environments to express, and environments change gene expression through epigenetic mechanisms
• Developmental plasticity means that early experience literally shapes the neural architecture of desire — but the brain retains significant capacity for change throughout life
• Cultural norms function as evolutionary environments, shaping what becomes familiar, sanctioned, and narratively available as desirable
• Neuroplasticity and the mere exposure effect show that attraction patterns are continuously influenced by what we encounter and are exposed to
• The Coolidge effect illustrates how "natural" drives interact with cultural containers, producing very different outcomes in different social contexts
• Lisa Diamond's longitudinal research demonstrates genuine sexual fluidity in a significant proportion of women — not as confusion, but as a real feature of human desire
• Testosterone and social behavior form a bidirectional feedback loop, not a one-way causal chain
• The co-evolutionary model integrates all of these findings into a framework that preserves the reality of both biological predispositions and cultural influence

For Nadia — and for all of us who have ever wondered which parts of our desires are "really us" — the co-evolutionary model offers an unsatisfying but honest answer: all of it is really you, and all of it has a history, and those two facts are not in conflict. Your desires emerged from your specific life, at the intersection of your biology and your experience. They are yours to inhabit, to reflect on, and — within limits that are real but not absolute — to shape.

The shift from "nature versus nurture" to "co-construction and feedback" is not merely a semantic upgrade. It changes what questions we ask, what evidence we accept, and what conclusions we can draw. A researcher who assumes the question is "how much is biology, how much is culture?" will design studies that try to partition variance — and will perpetually find that both contribute, in ways that don't add up cleanly. A researcher who assumes the question is "how do biology and culture interact to produce this attraction pattern, in this developmental context, for this population?" will design richer studies and get more informative answers. The second researcher will also, not incidentally, be harder to exploit by ideologues on any side who want a simple "it's natural" or "it's a choice" answer to settle political debates. Good science on attraction is inherently resistant to that kind of appropriation — not because it is politically neutral, but because its complexity cannot be reduced to the slogans either side wants.

Continue to Chapter 11: Attachment Theory and Adult Romantic Bonds — Part III opens with the question of how early relational experience structures adult love.