{"paper_id":"86a5714f-9786-4f42-aa19-ca109e503ed3","body_text":"Vol.:(0123456789)\nArchives of Sexual Behavior (2025) 54:3785–3791 \nhttps://doi.org/10.1007/s10508-025-03331-y\nCOMMENTARY: HOW MANY SEXES ARE THERE? HOW MANY GENDERS ARE THERE?\nThe Spectrum of Sex and Gender\nLinda Arrighi1 \nReceived: 29 August 2025 / Revised: 22 September 2025 / Accepted: 23 September 2025 / Published online: 18 October 2025 \n© The Author(s) 2025\nSex and gender are intrinsic and ubiquitous aspects of the \nhuman experience. Right after we make our entrance in the \nworld, and often even when we are still in the womb, our \nexistence is tied to a specific sex and/or gender—signaled \nby the color of the cake at a gender reveal party, the color of \nthe decorations at a baby shower, or the joyous calls of “It’s \na boy!” or “It’s a girl!” Although sex and gender have been \nshown to overlap (e.g., sex and gender likely correspond \nin individuals who identify as cisgender; Veldhuis et al., \n2024) and intersect (e.g., both sex and gender contribute to \nperformance in a few specific cognitive tasks; Cartier et al., \n2024; Kheloui et al., 2023) in certain contexts, there are \nsome important distinctions to be made between the two. \nSex is related to someone’s anatomy and physiology and is \nassigned at birth upon clinical observation of (primarily) \nexternal genital organs (King, 2022) and is, for this reason, \nalso referred to as (birth-)assigned sex or sex registered at \nbirth. The sex someone can be assigned at birth is among \none of the following three options: male, female, and \nintersex but there are also other ways in which sex can \nbe determined biologically beyond clinical observation \nat birth, for example through examining chromosomes \nor hormone levels (King, 2022). The concept of gender \nidentity, also referred to as affirmed gender, instead relates \nto how someone conceptualizes and expresses their own \ngender (Morgenroth & Ryan, 2018). It has been shown that \nsomeone’s own concept of their gender emerges during early \nchildhood through interactions with family and peers, and is \ngenerally stable from 3 to 5 years of age onwards (Steensma \net al., 2013). Gender is both an important aspect of the \nself as well as an extremely salient aspect of our gendered \nsociety—it determines how we present ourselves to those \naround us and how we are perceived and treated.\nThe fact that sex and gender do not correspond in all \nindividuals makes it critical to distinguish them. For instance, \nsex and gender likely do not correspond in individuals who \nidentify as transgender, and intersex individuals’ gender \nidentity may be subjective and dependent on one’s own \ntraits and experiences (Thorne et al., 2019; Veldhuis et al., \n2024). The assumption that the concepts of sex and gender \nare interchangeable is rooted in biological determinism and \nessentialist ideas (van Anders, 2024). These ideas argue \nthat our gender is handed to us the moment we are born and \nstrictly the same as our assigned sex—completely excluding \nthe possibility that our sociocultural environment can have \nany effect on our concept of self. These essentialist ideas \nare also often accompanied by persistent gender stereotypes, \nrooted in the assumption that people of different sexes and \ngenders are biologically different in their traits and talents \n(Brescoll et al., 2013).\nA recent example of biological determinism and \nessentialism comes from Trump’s January 2025 inauguration \nspeech and executive order. As Zucker (2025) noted, Trump, \nin his inauguration speech, first declared that “There are only \ntwo sexes: male and female” and later that “There are only \ntwo genders: male and female” (CNN, 2025). This indicated \na perfect conflation of sex and gender as well as an implicit \nassumption that gender is biologically determined. In the \nexecutive order, shortly after, it was stated that “The sex \nof a human, female or male, is determined genetically at \nconception” (Department of Health & Human Services, \n2025), which is inaccurate in multiple ways. First, the \nassumption that sex is binary is driven by outdated ideas and \nscientifically inaccurate, as will be discussed in more detail \nin the latter part of this commentary. The statement is also \nuntrue based on the timing of sexual differentiation during \nfetal development, which is initiated at around 8–9 weeks \nof gestation rather than at conception (McCarthy, 2010; \nMcCarthy et al., 2018).\nThe executive order also stated that “A person’s sex \nis unchangeable and determined by objective biology” \n(Department of Health & Human Services, 2025) and \nincluded definitions of the terms male, female, man, and \n * Linda Arrighi \n linda.arrighi@durham.ac.uk\n1 Department of Psychology, Durham University, South Road, \nDurham DH1 3LE, UK\n\n3786 Archives of Sexual Behavior (2025) 54:3785–3791\nwoman which clearly demonstrated an assumption that sex \nand gender (1) are one and the same and (2) reflect essential \nand biological characteristics we are born with. These ideas \nperpetuate sex/gender stereotypes and can be extremely \ndamaging, hurtful, and exclusionary of individuals whose \nsex and gender do not correspond, or are outside the sex/\ngender binary (Howansky et al., 2022).\nAnother reason that makes it critical to distinguish sex \nand gender is that numerous aspects of health and disease \nintersect with either sex or gender, and sometimes with both \n(Gesensway, 2001; Gillies & McArthur, 2010; McCarthy \net al., 2012; Wierenga et al., 2023). For instance, bodily \nchanges through the teenage years (e.g., menstruation and \nassociated conditions, such as endometriosis) are sex-specific \n(Adler et al., 2024). The prevalence, presentation, and treat-\nment of certain conditions are also sex-specific. For exam-\nple, as the symptoms associated with myocardial infarction \nand the efficacy of certain treatments differ between males \nand females (Ferry et al., 2019), physicians need to consider \ntheir patients’ sex to ensure appropriate and timely interven-\ntion. From just these few examples, it is glaringly obvious \nhow accurately and consistently measuring someone’s sex—\nseparate from gender—is necessary to timely diagnosis and \nsometimes lifesaving in health contexts.\nIn certain clinical contexts, it may be useful to measure \nsomeone’s gender alongside their sex. For example, the \nprevalence and presentation of mental health and neurodi-\nvergent conditions differs across people of different sexes \nand genders. These differences are likely the result of the \ncombination of sex-specific neurological susceptibility and \ngender-specific adaptations to the sociocultural environ-\nment (Wierenga et al., 2023), including persistent stereo-\ntypes related to how people of different sexes and genders are \nexpected to behave. For example, it is assumed that mask -\ning in autistic females and women and, more generally, sex/\ngender differences in autism presentation exist because there \nare two distinct autism phenotypes (male and female). Differ-\nences in presentation are instead likely attributable to gender \nstereotypes and the assumption that there are distinct types \nof autism may be detrimental to timely diagnosis and is not \nreflected in the lived experiences of autistic people (Pearson \n& Rose, 2021, 2023). In these instances, knowing an indi-\nvidual’s sex and gender is important for accurate diagnosis \nand treatment (where appropriate). Asking for people’s sex \nand gender is easy to implement and quick to administer, but \nstill not the standard protocol in medical settings, where sex \nand gender are often conflated and terminology such as male/\nman and female/woman are used interchangeably, as noted \nby McCartney and Bewley (2025). Sex and gender have been \nat times conflated in research and academic settings as well \n(Cameron & Stinson, 2019).\nThis journal’s Editor seems to share the frustration with \nthe conflation of sex and gender (Zucker, 2025). Notably, \nsparked by the previously discussed inaugural speech and \nexecutive order by Donald Trump (CNN, 2025; Department \nof Health & Human Services, 2025), the call that this com-\nmentary is responding to specifically mentioned two ques-\ntions: (1) How many sexes are there? and (2) How many gen-\nders are there? Historically, the concepts of sex and gender \nhave been socially constructed, understood, and accepted as \nbinary, i.e., our traditional cultural notion of the presence \nof meaningful differences between men and women has \nin turn shaped our interpretation of biological evidence as \nsupporting rather than refuting sexual dimorphism (Hyde \net al., 2019; Morgenroth & Ryan, 2018). Recent research has \ninstead challenged the binary notions of sex and gender—\nhighlighting how they oversimplify reality, are exclusionary, \nand have remarkable economic costs for our society.\nSpecifically for sex, recent reports in the fields of toxicol-\nogy and neuroendocrinology have recommended moving \naway from conceptualizing sex as a binary, as assigning sex \nout of a few options negates the large extent of individual \nvariability (King, 2022; Smiley, 2024). These individual \ndifferences have been observed at the genetic, molecular, \nhormonal, anatomical, physiological, psychological, and \nbehavioral level within what we would clinically and soci-\netally categorize as belonging to the same sex category, as \nwell as across categories (Bhattacharyya, 2024; Hyde et al., \n2019; Smiley, 2024). Critically, the extensive individual \nvariability makes it extremely difficult and sometimes inac-\ncurate to fit all individuals within either of the three neat \nand practical categories of male, female, and intersex (King, \n2022). For example, most females have two X chromosomes \nand most males an X and a Y chromosome, but there are \naround 40 combinations, also defined as intersex conditions \nor differences in sex development, that diverge from this, \nand sometimes chromosomes are incomplete or inactivated \n(Jones, 2018). This can lead to extremely variable presen-\ntations across individuals (Carpenter, 2018; Jones, 2018; \nMoran, 2020).\nWhile scientific advancement has highlighted the extent \nand abundance of sex variability, the definition of sex is still \ndebated and part of the scientific community recognizes and \naccepts the gametic definition of sex, i.e., sex is determined \nby the gametes present in the individual, sperm, or eggs \n(Parker et al., 1972). Because only two gametes exist, this \ndefinition of sex is necessarily binary. Within this definition, \nany divergence in terms of chromosomes and/or gametes is \nconsidered an anomaly rather than evidence for the exist-\nence of more than two sexes (e.g., King, 1945). However, \nthe gametic definition of sex implicitly reduces individuals \nto their capability to reproduce and conceptualizes evolution-\nary success as being exclusively reliant on reproduction. In \ncontrast with this notion, research has shown that certain \nindividuals (including intersex individuals) may adapt and \npass on their genes through kin selection (e.g., helping own \n\n3787Archives of Sexual Behavior (2025) 54:3785–3791 \nrelatives to raise children) rather than direct reproduction—\nthus diversifying how evolution may take place (Hamilton, \n1964; Sun, 2024). Additionally, the gametic definition of \nsex is exclusionary, leads to stigma and alienation of inter -\nsex individuals, and overlooks the variability and overlap in \nphysiology and presentation across individuals who would be \ncategorized as the same sex, as well as across sexes.\nFor example, it has been shown that conditions that are \nrelatively common such as polycystic ovary syndrome (it is \nestimated that up to one in five women have this condition, \nwith similar estimates [16.6%; Lauritsen et al., 2014] when \nusing the Rotterdam criteria; Teede et al., 2010) are associ-\nated with higher testosterone levels than would generally be \nexpected in females (Bhattacharyya, 2024; Schattmann & \nSherwin, 2007). Alongside this, secondary sex character -\nistics such as body hair may be more aligned with a typical \nmale presentation. Another example comes from research \nmeasuring hormone levels suggesting that there is a moderate \ndegree of overlap in males’ and females’ hormone profiles \n(e.g., estradiol and progesterone), such that the only binary in \nterms of meaningful differences in hormonal profiles would \ncomprise “pregnant females” and “everyone else” (Hyde \net al., 2019; Tulchinsky et al., 1972). Due to large individual \nvariability, hormone levels are not and should not be used to \ncategorize individuals as more or less male (or female) than \nothers (Hotine, 2021).\nOverall, the research presented suggests that historically \nendorsed binary classifications of sex (e.g., stating that all \nindividuals are either male or female) are, at a minimum, \nbiologically inaccurate (Bhattacharyya, 2024). While the \naddition of an intersex category demonstrates an attempt at \ninclusion, it others individuals who do not meet the implicit \nbinary expectations of sex, i.e., how one should look like to fit \nthe label of male or female. The categorization of individuals \nas male, female, and intersex, although widely recognized \nas appropriate, is, at least partly, a biased interpretation of \nanatomy and physiology influenced by longstanding binary \nviews of sex and gender (Hyde et al., 2019; Morgenroth & \nRyan, 2018). To ensure scientific accuracy and true inclu -\nsion, it may be more appropriate to define sex as a spectrum \nwhich entails several traits (King, 2022), from the genetic \nto the behavioral, with the more typical male and female \npresentations at either end.\nThe newer concept of gender has been, similar to that of \nsex, socially constructed as a binary (Morgenroth & Ryan, \n2018), including only the identities of man and woman \nand associating specific characteristics and talents to each. \nHowever, reports have shown that there are countless \nmore gender identities and extensive variability in gender \nexpression, gender fluidity, and choice of pronouns across \nindividuals (Thorne et al., 2019; Yarbrough, 2018). For \nindividuals whose gender generally matches their assigned \nsex (i.e., likely to identify as cisgender), the experience and \nexpression of their own sex and gender may be straightforward \nand untroubled. In contrast, individuals whose gender differs \nfrom their assigned sex and/or from binary categories of \nman and woman (i.e., likely to identify as transgender) may \nexperience distress about this mismatch as well as society’s \nexpectations and rules around gender identity and expression \n(Cooper et al., 2022; Ristori & Steensma, 2016).\nIndeed, there is a body of literature dedicated to under -\nstanding the experience of gender dysphoria (Ristori & \nSteensma, 2016; Steensma et al., 2013), including in neuro-\ndivergent individuals, who may deal with multiple intersect-\ning challenges and find it especially difficult to subscribe to \nsocietal expectations of gender (Cooper et al., 2022; Kourti & \nMacLeod, 2019). Across this literature, it has been reported \nthat the lack of societal acceptance is a significant source \nof distress for gender dysphoric and transgender individu-\nals (Cooper et al., 2022). To ensure representation and true \ninclusion, gender may also be best categorized as a spectrum, \nwith the more typical identities of man and woman (or, if \npreferred, masculinity and femininity) at either end.\nCategorizing both sex and gender on a spectrum rather \nthan through discrete categories stems from similar concerns, \nincluding (1) a need for scientific accuracy and (2) a desire \nto include and welcome individual variability. However, \ncategorizing sex as a spectrum and gender as a spectrum \nmay not be equally well received. Recent years have seen \nincreased recognition and understanding of gender diversity \nacross the general population (Hammack & Wignall, 2023), \nmaking the concept of gender as a spectrum relatively more \ndigestible and acceptable than that of sex as a spectrum. This \nis because a good portion of the general population, espe-\ncially in Western countries, would agree that while gender \ncan be a spectrum, sex is untouchably binary (Bhattacharyya, \n2024). As discussed above, categorizing sex as a spectrum \nis more scientifically accurate and hence closer to biologi-\ncal reality. Notably, a common essentialist argument that is \noften lumped together with the conflation of sex and gender \nis that conceptualizing sex as a spectrum denies biological \nreality. Essentialists may use statements such as “there are \nonly two sexes,” “you cannot change your sex,” and “but you \nare really a male (or female)” which, while not completely \ninaccurate or always intended to be hurtful, may invalidate \nthe experiences and the identity of transgender individuals \n(e.g., Hotine, 2021).\nIn this vein, holding onto binary and deterministic sex has \nbeen, especially recently, the reason for divisive and often \nrage-fueled debates in the media, online, and in politics \nabout, among others, the definitions of sex, gender, man, \nwoman, male, and female. A recent example has culmi-\nnated in the Supreme Court ruling in the UK declaring that a \n“woman” is an individual who is assigned female at birth, and \nnot an individual who identifies as a “woman” on their Gen-\nder Recognition Certificates (Supreme Court of the United \n\n3788 Archives of Sexual Behavior (2025) 54:3785–3791\nKingdom, 2025). Although maybe not directly implied by \nthis statement, this suggests that someone who identifies as \na “woman” but was not assigned female at birth is not a real \nwoman—which can be an incredibly hurtful and invalidating \nstatement for transgender women. The recent increased atten-\ntion and debates on transgender rights has led to increased \nrates of discrimination and violence against transgender peo-\nple in Europe, with a recent study showing that 58% of the \n19,669 transgender individuals surveyed reported discrimi-\nnation and 40% reported being attacked at least once in the \nprevious year (Evje et al., 2024). Transgender individuals \nwere shown to experience more discrimination and violence \nthan the 118,543 cisgender lesbian, gay, and bisexual (LGB) \nindividuals surveyed, 40% of whose reported discrimination \nand 25% reported violence in the previous year. Notably, the \nrates of discrimination and violence experienced by transgen-\nder individuals were higher than those experienced by cisgen-\nder LGB individuals irrespective of the countries' rankings \nof LGBTQIA+ rights (Evje et al., 2024). These findings hint \nat a worrying disconnect between the growing acceptance of \nsex and gender diversity across the scientific community and \nthe notions and stereotypes commonly held by the general \npopulation.\nBeyond the damage to individuals, holding onto outdated \nbinary concepts of sex and gender has tangible and meas-\nurable costs across multiple sectors. For example, assum-\ning sex is binary in healthcare settings can lead to increased \nmortality, higher treatment costs, delayed diagnoses or mis-\ndiagnoses, and lower quality of life (e.g., All Party Parlia-\nmentary Group on Endometriosis, 2020; Kersey, 2024; Wu \net al., 2018). As research and care protocols are designed \nand carried out based on the binary of male and female, with \nmale often being the default, billions are spent annually and \nresearch funding is wasted due to (1) the longer time needed \nto reach an appropriate diagnosis for conditions that differ -\nently or disproportionally affect people of different sexes/\ngenders, and (2) the lack of effective treatment options for \nconditions that differently or disproportionally affect people \nof different sexes/genders (Kersey, 2024; World Economic \nForum, 2024). Additionally, higher mortality and lower \nquality of life are preventable consequences of intersex and \ntransgender people delaying or avoiding medical care due to \ndiscrimination and/or dismissive interactions with healthcare \nprofessionals (Baugher et al., 2024; Kcomt et al., 2020; Seel-\nman et al., 2017). Sex/gender health gaps lead to an enormous \nfinancial burden—it is estimated that addressing sex/gender \ngaps in cardiovascular disease care protocols could add about \n$28 billion to the USA economy each year by 2040, while \nalso providing at least 1.6 million additional years of quality \nlife (Kersey, 2024). More generally, conducting research that \ncan help narrow the sex/gender health gap has the potential \nto increase the global economy by over $1 trillion each year \nby 2040 (World Economic Forum, 2024).\nThese preventable costs are particularly tangible and \ntroubling with the recent censorship campaign to research \ninvestigating “gender” and “diversity” in the USA (Graham \net al., 2025) and the Supreme Court ruling in the UK declar-\ning that sex is binary and biologically determined, and that \nprotected characteristics are defined through assigned sex and \nnot Gender Recognition Certificates (Supreme Court of the \nUnited Kingdom, 2025). This redirection of funding efforts \nand negative attitudes toward sex-/gender-related research \nis likely to worsen the financial burden of under-research-\ning conditions that disproportionately or differently affect \nfemales, women, intersex, and transgender individuals.\nIn workplaces and education, assuming sex and gender \nare binary and implementing binarily gendered policies (e.g., \nuniforms, dress codes, and restrooms) may lead to discrimi-\nnation and alienation of transgender and intersex employees \nand students, who may resign or be less motivated to get \ngood grades (Kosciw et al., 2021). News outlets in the UK \nhave been documenting the increased harassment following \nthe Supreme Court ruling suggesting that restroom access is \ndetermined by an individual’s assigned sex rather than their \naffirmed gender (Supreme Court of the United Kingdom, \n2025). An example is a report of a cisgender woman being \nchallenged in women’s restrooms due to other users suspect-\ning her of being transgender because of her ambiguous pres-\nentation (Brooks, 2025).\nIndividuals resigning from jobs or withdrawing from their \nstudies due to discrimination and harassment, as well as a loss \nof human potential, has remarkable financial costings related \nto companies being involved in costly sex-/gender-related \ndiscrimination lawsuits and replacing employees who resign \n(U.S. Equal Employment Opportunity Commission, n.d.). \nObtaining lower grades in school and resigning from jobs \ndue to discrimination may, in turn, result in lower lifetime \nearnings and increased reliance on assistance programs and \nbenefits systems—something which can have notable public \ncosts (Badgett et al., 2019). From just these few examples, \nit becomes clear that there are serious financial, legal, and \nhuman costs that can be prevented by moving away from \nbinary concepts of sex/gender.\nIn sum, sex and gender are concepts with important dis-\ntinctions as well as intersections, especially in health and \ndisease, but the simple answer to the questions (1) How many \nsexes are there? and (2) How many genders are there? is that \nit is inappropriate to answer either of these questions with a \nnumber because both concepts are better conceptualized as \na spectrum comprising of several traits, rather than a series \nof discrete and countable categories. This conceptualization \nis more scientifically accurate than traditional binary clas-\nsifications, can reduce the extensive operational and financial \ncosts caused by holding onto rigid sex/gender binaries, and \nmay be a catalyst for acceptance and inclusion of individuals \nof all sexes and genders.\n\n3789Archives of Sexual Behavior (2025) 54:3785–3791 \nAcknowledgements I thank M.H. and S.H. for their helpful input on \nan earlier draft of this manuscript.\nAuthor Contributions Linda Arrighi has contributed to the conceptu-\nalization, writing—original draft, and writing—review and editing.\nFunding No funding was received to assist with the preparation of this \nmanuscript.\nDeclarations \nConflicts of interest None.\nEthics Approval Not applicable.\nOpen Access This article is licensed under a Creative Commons Attri-\nbution 4.0 International License, which permits use, sharing, adapta-\ntion, distribution and reproduction in any medium or format, as long \nas you give appropriate credit to the original author(s) and the source, \nprovide a link to the Creative Commons licence, and indicate if changes \nwere made. 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Archives of \nSexual Behavior, 54(5), 1687–1689. https:// doi. org/ 10. 1007/  \ns10508- 025- 03190-7\nPublisher's Note Springer Nature remains neutral with regard to \njurisdictional claims in published maps and institutional affiliations.","source_license":"CC-BY-4.0","license_restricted":false}