“The science is clear. The stigma is learned. And the only thing missing is the courage to teach honestly.”
By Andrew Klein
Dedication: To my wife — who knows that trust is not a transaction, and that love is not a mystery to be solved, but a gift to be given.
Introduction: The Most Misunderstood Human Behaviour
Human sexuality is simultaneously the most discussed and most misunderstood aspect of our nature. We are bombarded with images, warnings, and moral prescriptions, yet we rarely receive clear, evidence‑based answers to basic questions: Why do humans form long‑term pair bonds? Why is physical touch so central to our wellbeing? Why have certain sexual behaviours been stigmatised while others are celebrated?
This article is not a moral argument. It is an evolutionary and physiological one. Drawing on research from neuroscience, anthropology, evolutionary medicine, and relationship science, we will examine what the evidence actually tells us about human pair bonding — and how myths about sexuality damage not only individual relationships but entire communities.
I. The Neurobiology of Pair Bonding: Why We Need Connection
The human capacity for long‑term attachment is not a cultural invention. It is hardwired.
Studies of pair bonding in monogamous species such as prairie voles (Microtus ochrogaster) have revealed the neural circuits that underpin selective attachment between individuals. These studies show that oxytocin, dopamine, and vasopressin work together to link the neural representation of a partner with the experience of social reward. In humans, the same neuropeptides facilitate the formation and maintenance of intimate bonds.
Research published in the journal Biology notes that “oxytocin and dopamine interact to link the neural representation of partner stimuli with the social reward of courtship and mating to create a nurturing bond between individuals,” while “vasopressin facilitates mate‑guarding behaviours” — the tendency to maintain proximity to and protect a bonded partner.
These are not cultural habits. They are biological imperatives.
Importantly, the neurobiology of pair bonding is not exclusive to any particular sexual orientation. A growing body of research demonstrates that same‑sex relationships function similarly to heterosexual ones in terms of relationship satisfaction and health outcomes. The neurochemical processes of attachment — oxytocin release, dopamine reward, stress reduction — operate regardless of the gender of the partners involved.
II. The Evolution of “Marking”: Semen as a Chemical Signal
One of the most misunderstood aspects of human sexuality is what might colloquially be called “marking” — the deposition of semen on or in the body. Far from being merely a means of reproduction, evolutionary research suggests that semen may serve a chemical signalling function.
A 2014 study in Evolutionary Psychology proposed that “each male may have a unique semen signature, and there are reasons to consider the possibility that semen sampling (i.e., being inseminated by different prospective mates during courtship) may be part of an evolved female mate assessment strategy”.
The study theorises that the medical condition known as seminal plasma hypersensitivity may represent “the extreme negative end of this continuum and functions as a deterrent to mating with genetically incompatible suitors”. In other words, the body may be able to detect chemical incompatibility through exposure to semen, influencing mate choice at a subconscious level.
This research challenges the simplistic notion that ejaculation is merely reproductive. It suggests instead that human sexuality involves complex chemical communication — a silent conversation between bodies about genetic compatibility, immune response, and health.
Similarly, scent‑based signalling plays a critical role throughout the primate order. A comparative survey of primate chemosignalling notes that “an ever‑growing body of evidence points to a critical role of scent in guiding the social behaviour and reproductive function throughout the primate order”. Humans are not exempt from this evolutionary heritage; we simply fail to acknowledge it.
III. Trust and Vulnerability: The Mutual Gift of Surrender
Perhaps the most profound aspect of consensual sexual activity is the mutual vulnerability it requires.
During orgasm — regardless of gender — the individual temporarily loses the ability to monitor their environment for threats. Dopamine, oxytocin, and endorphins flood the brain, creating a state of focused pleasure that bypasses the usual vigilance mechanisms. This is not a design flaw. It is a trust signal.
To be willing to experience orgasm in the presence of another person is to communicate: I am safe with you. I do not need to watch for danger because I trust you to protect me.
This mutual vulnerability is a cornerstone of pair bonding. Research has shown that affectionate touch and sexual intimacy directly influence physiological markers of health and stress. A 2025 study published in JAMA Psychiatry found that physical intimacy, when combined with oxytocin release, accelerated wound healing and lowered cortisol levels — the body’s primary stress hormone.
The study’s key findings were striking:
· Oxytocin amplified the healing effects of affectionate touch. Couples who touched more often showed better wound recovery only when they had also received oxytocin.
· Sexual intimacy was linked to lower cortisol levels. Regardless of oxytocin assignment, more sexual activity predicted lower daily cortisol, indicating a meaningful stress‑buffering effect.
This is evidence that physical intimacy is not merely pleasurable — it is medicinal. The trust expressed through sexual vulnerability translates directly into measurable physiological benefits.
IV. The Clitoris: A Case Study in Scientific Neglect
If there is a single organ that demonstrates the failure of sex‑positive education, it is the clitoris.
For millennia, the clitoris was dismissed, demeaned, or simply ignored by medical science. Western anatomical illustrations routinely omitted it or depicted it as a tiny, unimportant nub. Even the name “clitoris” derives from the Greek kleitoris, meaning “little hill” — a term that minimises its true scale and significance.
In fact, the clitoris is an iceberg. Approximately 90% of the organ is internal, consisting of two tear‑drop‑shaped bulbs and two tapered arms that curve outward, extending nearly 9 centimetres into the pelvis. Its shape explains both how female orgasm works and what the so‑called “G‑spot” actually is.
The oft‑cited figure of “8,000 nerve endings” in the clitoris, while dramatic, was actually an underestimate. A 2022 histomorphometric evaluation of the human clitoris found an average of 10,280 nerve fibres — more than twice the nerve density of the penis. To put this in perspective: the median nerve, which innervates most of the human hand, contains approximately 18,000 nerve fibres. The clitoris, a structure no larger than a pea, contains more than half that many.
This remarkable density has profound implications. The clitoris is not an afterthought. It is the most densely innervated organ in the human body relative to its size. Its sole biological function is pleasure.
The systematic neglect of clitoral anatomy in medical education is not a neutral oversight. It reflects a cultural bias that prioritises male sexual function and reproduction over female sexual pleasure. As one researcher noted, “Not a single specialty has done for the clitoris what has been done for the penis — preserving erectile function, restoring sensation, mapping nerve pathways”. This is not medicine. It is institutional neglect.
V. The Health Benefits of Consensual Intimacy
A 2025 review published in the journal Sexual and Relationship Therapy synthesised research on how sexual activity — including intimate touch, solo sex, and partnered sex — improves physical and mental health.
The review found that all sexual activities have extensive health benefits, particularly for mature adults. Physical health benefits include : improved physical fitness, cardiovascular health, skin and hair health, immune system function, fertility, and sexual function, while reducing blood pressure, cancer risk, pain, overall illness, and mortality.
Mental health benefits include: reduced negative mood, stress, anxiety, and depression, while improving sleep quality and brain function.
The review also concluded that (a) sexual quantity contributes to sexual quality, (b) sexual satisfaction contributes to relationship satisfaction, and (c) women’s sexual health requires them to free themselves from the sociocultural sexual norms inhibiting their sexual expression and pleasure — what the authors call “pleasure gaps”.
The implications are clear: sexual health is not a luxury. It is a foundational component of overall wellbeing.
VI. Pair Bonding Across the Spectrum
Pair bonding is not confined to heterosexual monogamy. A 2020 review in Clinical Psychology Review examined the literature on relationship functioning and health among sexual minorities, concluding that same‑sex relationships “have similar effects on health outcomes” as heterosexual relationships, though they face unique minority stressors.
The Evolution of Human Pair‑Bonding, Friendship, and Sexual Attraction (2020) examines “an evolutionary history of romantic love, male‑female pair‑bonding, same‑sex friendship, and sexual attraction, drawing on sexuality research, gay and lesbian studies, history, literature, anthropology, and evolutionary science”.
Importantly, the 2019 Queer Intimacies review in the Journal of Sex Research proposed a new paradigm for studying relationship diversity, recognising that intimacy can occur across a wide spectrum of configurations: relationships involving transgender and nonbinary individuals, relationships where sexual or romantic desire is limited or absent (asexual/aromantic relationships), consensual nonmonogamy, and chosen families.
The neurobiological mechanisms of attachment — oxytocin, dopamine, vasopressin — do not discriminate based on gender or relationship structure. They respond to connection.
VII. How Myths Undermine Relationships and Community
If the science of pair bonding is so clear, why do so many people struggle with intimacy? The answer lies in myths.
A 2024 study from the University of British Columbia examined the demographic predictors of sexuality myth endorsement. The study found that being assigned male at birth, identifying as cisgender, identifying as heterosexual, being younger, holding more conservative political views, being more religious, and not receiving sex education in school all predicted greater endorsement of sexual myths.
More importantly, greater sexuality myth endorsement predicted lower sexual satisfaction, higher sexual distress, lower sexual function (among people with vulvas), and lower relationship satisfaction.
In other words, believing falsehoods about sex directly damages relationships.
Common myths include:
· That certain sexual behaviours are “unnatural” or “deviant” (contradicted by cross‑cultural and historical evidence)
· That the clitoris is unimportant or that female pleasure is secondary to reproduction (contradicted by neuroanatomy)
· That same‑sex attraction is a disorder or a choice (contradicted by decades of research)
· That sexual frequency is a measure of relationship health (contradicted by studies showing that satisfaction, not frequency, predicts wellbeing)
· That sexual activity should be limited to reproduction (contradicted by the evolution of the clitoris, which has no reproductive function)
These myths are not harmless. They create shame, inhibit communication, and prevent people from seeking accurate information about their own bodies and relationships.
VIII. Stigma as a Community Poison
The impact of sexual stigma extends beyond individual relationships. Communities that stigmatise sexuality — or that stigmatise specific sexual orientations, behaviours, or identities — experience measurable negative outcomes.
Research on the “monogamy‑superiority myth” demonstrates that people in consensually nonmonogamous (CNM) relationships often face stigma, social disapproval, and systemic barriers — from difficulty disclosing their relationship status to concerns about discrimination in healthcare, workplaces, and legal systems.
Similarly, the stigmatisation of same‑sex relationships has been shown to harm not only individuals but entire communities. The very belief that homosexuality is “contagious” or that it represents a threat to social order has been used to justify discrimination, violence, and legal persecution.
These beliefs are not supported by evidence. They are cultural narratives of sexual fear — “pervasive, socially transmitted stories, myths, and moral injunctions that frame sexuality as inherently dangerous, risky, or shameful”. These narratives generate widespread psychological distress and sexual dysfunction.
IX. Romantic Behaviour as Pair Bonding Reinforcement
“Nesting” is not merely a practical activity. It is a pair bonding behaviour.
Research on pair bonding across species has demonstrated that behaviours that create a shared environment — preparing a home, acquiring shared resources, planning for the future — activate the same neural circuits (oxytocin, dopamine, vasopressin) as direct physical intimacy.
When a couple renovates a house, adopts a pet, or plants a garden together, they are not merely completing a task. They are reinforcing their bond. The shared project becomes a shared symbol of the relationship.
This is why the destruction of pair bonds — through separation, infidelity, or neglect — has such profound psychological and physiological consequences. Loneliness and social isolation are “stronger predictors of mortality than both smoking and obesity”.
X. Conclusion: Toward Honest Education
The evidence is clear. Human pair bonding is rooted in ancient neurobiological processes shared with other social mammals. Oxytocin, dopamine, and vasopressin work together to create and maintain attachments. Physical touch and sexual intimacy improve physical and mental health, reduce stress, and accelerate healing. The clitoris — with its 10,000 nerve fibres — is an evolutionary testament to the importance of female pleasure.
None of this is controversial among researchers. It is simply not widely taught.
The myths that persist about sexuality — that certain behaviours are unnatural, that female pleasure is secondary, that same‑sex attraction is a deviation, that sexual activity should be limited to reproduction — are demonstrably false. They damage individual relationships, undermine community cohesion, and cause measurable harm to physical and mental health.
What is needed is not more moralising, but more honest education. Science‑based, inclusive, and free from stigma.
Pair bonding is not a mystery. It is a physiological reality. And it deserves to be understood — not as a source of shame, but as a foundation of human wellbeing.
Andrew Paul Klein
References
1. Blumenthal, S. A., & Young, L. J. (2023). The Neurobiology of Love and Pair Bonding from Human and Animal Perspectives. Biology, 12(6), 844.
2. McGraw, L., Székely, T., & Young, L. J. (2010). Pair bonds and parental behaviour. In Social behaviour: Genes, ecology and evolution, 271-301. Cambridge University Press.
3. Gallup, G. G., & Reynolds, C. J. (2014). Evolutionary Medicine: Semen Sampling and Seminal Plasma Hypersensitivity. Evolutionary Psychology, 12(1), 245-250.
4. Peters, B., et al. (2022). Quantitative analysis of clitoral dorsal nerve fibers. Presented at Sexual Medicine Society of North America annual meeting.
5. Kim, K. H. (2025). Sex for health? How sexual activity improves physical and mental health and beyond. Sexual and Relationship Therapy, 3-45.
6. Newcomb, M. E., et al. (2020). Romantic Relationships and Sexual Minority Health: A Review and Description of the Dyadic Health Model. Clinical Psychology Review, 82, 101924.
7. Hammack, P. L., Frost, D. M., & Hughes, S. D. (2019). Queer Intimacies: A New Paradigm for the Study of Relationship Diversity. Journal of Sex Research, 56(4-5), 556-592.
8. O’Kane, K. M. K. (2024). Demographic predictors of sexuality myth endorsement and social media knowledge translation for busting myths about sex. UBC Theses and Dissertations.
9. Suvilehto, J. T., et al. (2025). Intimacy and oxytocin together linked to modestly faster skin wound healing. JAMA Psychiatry.
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