In biology, a hermaphrodite is an organism that produces both eggs and sperm, either at the same time or at different stages of life. The term is accurate and uncontroversial when applied to snails, earthworms, certain fish, and many flowering plants. Where it fell out of favor was in human medicine. Humans, as a species, do not produce both types of reproductive cells, so applying the word to people born with atypical sex anatomy was always a biological mislabel. Over the past two decades, medical and advocacy communities have moved away from “hermaphrodite” for humans, though the replacement terminology itself remains a source of debate.
How Hermaphroditism Works in the Animal Kingdom
True hermaphroditism is widespread in the animal world, though it takes several distinct forms. Simultaneous hermaphrodites carry functioning male and female reproductive tissues at the same time and can produce both eggs and sperm during the same period of their lives. Many snails, slugs, and flatworms fall into this category. The great pond snail, for instance, maintains both sexual functions concurrently, and recent genomic work suggests this dual-sex capability requires an expanded set of signaling receptors so the body can regulate male and female reproductive processes without them interfering with each other.1PubMed Central. The genome of the simultaneously hermaphroditic snail Lymnaea stagnalis reveals an evolutionary expansion of FMRFamide-like receptors In a sense, being both sexes at once is harder to manage neurologically and hormonally than being one at a time.
Sequential hermaphrodites, on the other hand, switch sex during their lifetime. Clownfish are a familiar example: they are born male and the dominant individual in a group transitions to female. This is called protandry (male-first). Other fish, like many wrasses, start female and become male, which is protogyny (female-first).2PubMed Central. Sex Change in Clownfish: Molecular Insights from Transcriptome Analysis Some biologists argue that sequential sex change is distinct enough from true hermaphroditism that it should be classified separately, since the animal functions as one sex at a time rather than both simultaneously.3New Zealand Journal of Zoology. Hermaphroditism as a reproductive strategy for metazoans; some correlated benefits
Evolutionary analyses of fish reproductive systems show that separate-sex species (called gonochorists) represent the most stable evolutionary state. Simultaneous hermaphroditism appears to evolve rarely and most often arises from sequential hermaphroditism rather than directly from separate sexes. Once established, though, it tends to persist, being lost back to gonochorism only slowly.4PubMed Central. Switches, stability and reversals in the evolutionary history of sexual systems in fish Across the broader tree of life, transitions between hermaphroditism and separate sexes have occurred many times, following at least five recognizable evolutionary paths in one direction and two in the other.5Annual Review of Ecology, Evolution, and Systematics. Evolutionary Transitions Between Hermaphroditism and Dioecy in Animals and Plants
Why Hermaphrodite Does Not Apply to Humans
Humans are a strictly gonochoristic species: each individual develops gonads that produce either eggs or sperm, never both functional gamete types. Even in people born with ambiguous genitalia, mixed gonadal tissue, or chromosomal patterns that do not match typical male or female development, the body does not achieve the capacity to produce both eggs and sperm. A 2024 review in Integrative and Comparative Biology makes this point explicitly, noting that “hermaphrodite” is inappropriate for humans because the species developmentally cannot produce both types of gametes.6Oxford Academic. Hermaphrodite, Gonochorist, and More: Navigating the Complexities of Sex-Related Language in Biology
For a long time, medicine used “true hermaphrodite” to describe individuals with both ovarian and testicular tissue (a very rare condition), and “pseudohermaphrodite” for those whose external anatomy did not match their chromosomal or gonadal sex. These labels persisted in medical textbooks through most of the twentieth century. But the terminology was misleading at a biological level and stigmatizing at a personal one, and it eventually collapsed under both scientific and ethical pressure.
How Human Sex Development Creates Variation
To understand what was being mislabeled, it helps to know what typically happens during early development. For about the first six weeks after fertilization, the embryonic gonad is bipotential, meaning it has the capacity to develop in either the male or female direction. In embryos with a Y chromosome, a gene called SRY activates, triggering a cascade of signals that steer the tissue toward becoming testes. Key downstream genes like SOX9 amplify this signal, while competing pathways (including WNT4 and a gene called DAX1) push toward ovarian development.7PubMed Central. A Boolean network model of human gonadal sex determination The outcome depends on which pathway wins, and the timing matters: SRY expression peaks at a specific window, and SOX9 ramps up in parallel during testis formation.8Mechanisms of Development. Gene expression pattern SRY, SOX9, and DAX1 expression patterns during human sex determination and gonadal development
Once the gonads form, hormones take over. Testes produce androgens that masculinize the rest of the body. Ovaries follow a different hormonal path. But this multi-step process has many points where things can unfold differently. The chromosomes might be atypical (XXY, XO, or mosaic combinations). The SRY gene might be absent from a Y chromosome, or present on an X. The gonads might form partially in each direction. Hormone receptors might not respond normally. Each of these variations produces a different pattern of sex characteristics, and collectively they are what used to be labeled with “hermaphrodite” terms.
One concrete example: partial androgen insensitivity syndrome occurs in individuals with a 46,XY karyotype whose androgen receptors work less effectively than typical. The result can be genitalia that appear neither clearly male nor clearly female at birth, despite the presence of testes.9PubMed Central. Partial Androgen Insensitivity Syndrome and Congenital Adrenal Hyperplasia-A Case Report of the Coexistence of Two Rare Diseases in One Patient Congenital adrenal hyperplasia, which affects the adrenal glands rather than the gonads, can produce a different pattern of ambiguity in individuals with XX chromosomes. These are distinct conditions with distinct causes, which is part of why a single umbrella label like “hermaphrodite” was never a good fit.
The 2006 Consensus and the Rise of “DSD”
The formal break from older terminology came in 2006, when a task force of about fifty specialists from the European Society for Paediatric Endocrinology and the Lawson Wilkins Pediatric Endocrine Society published a consensus statement. They proposed replacing “hermaphrodite,” “pseudohermaphrodite,” and the general label “intersex disorders” with a new umbrella term: disorders of sex development, or DSD.10PubMed. Impact of the consensus statement and the new DSD classification system Under this framework, DSD was defined broadly as any condition present at birth in which genital anatomy is atypical relative to the person’s chromosomes or gonads.11PubMed. Disorders of sex development: a new definition and classification
The goals were partly clinical: “true hermaphrodite” became “ovotesticular DSD,” “male pseudohermaphrodite” became “46,XY DSD,” and “female pseudohermaphrodite” became “46,XX DSD.” These names are more precise. They tell a clinician something about the chromosomal basis of the condition rather than relying on a mythological figure to describe a patient’s anatomy.
But the shift was also a response to decades of patient testimony about the harm caused by loaded language. Being called a hermaphrodite in a clinical setting carried connotations of abnormality and otherness that went well beyond a diagnosis. The new system aimed to sound more neutral and medical.
The Debate That Followed
If the 2006 consensus resolved the “hermaphrodite” question, it opened a new one. Many intersex adults and advocacy organizations objected to “disorders of sex development,” arguing that replacing a stigmatizing label with the word “disorder” was not much of an improvement. Being intersex, in this view, is a natural variation in human biology, not a pathology that needs a disorder label. Some advocates pushed for “differences of sex development” (keeping the DSD abbreviation but swapping in a less medicalized word), while others preferred simply retaining “intersex” as a community identity term.
Sociological analysis of this shift has pointed out that the new DSD framework allowed medical professionals to reassert clinical authority over a set of conditions that intersex activists had been successfully reframing as social and civil-rights issues rather than strictly biological ones.12Emerald Insight. “DSD is a Perfectly Fine Term”: Reasserting Medical Authority through a Shift in Intersex Terminology In other words, the language change was not ideologically neutral. It served some interests better than others, and the people most directly affected were not all on board.
In current practice, the landscape is a patchwork. Most peer-reviewed clinical literature uses “DSD.” Many patient-facing organizations use “differences of sex development” or “intersex” depending on context. Some individuals prefer intersex as an identity label. Others find it just as unwanted as older terms and prefer to be described by their specific diagnosis. The lack of a single accepted term reflects a genuine unresolved tension between medical precision, personal identity, and political framing.
Psychological and Social Impact
Regardless of which term is used, the experience of being born with atypical sex characteristics carries psychological weight that goes well beyond language. A national study of intersex adults in the United States found high rates of suicidality and poor mental health, which the researchers linked to stigma, discrimination, and negative experiences in healthcare settings.13PubMed Central. A national study on the physical and mental health of intersex adults in the U.S. These are people who often endured invasive medical examinations in childhood, may have been subjected to surgical procedures they did not consent to, and grew up hearing their bodies described in pathologizing terms.
Research on clinical care preferences has emphasized that the most valued aspects of care from the perspective of individuals with DSD and their families are straightforward: good communication between the care team and the patient or family, education about the condition, and incorporation of the family’s own values into treatment decisions.14PubMed Central. Preferences in Clinical Care of Individuals With Differences of Sex Development These may sound obvious, but they stand in contrast to a historical model in which clinicians often made decisions quickly, sometimes withholding information from parents or recommending surgery to “normalize” an infant’s anatomy before the child could participate in the decision.
The Surgical Controversy
One of the sharpest ongoing ethical debates in this area concerns cosmetic genital surgeries performed on intersex infants and young children. These are not surgeries to address a medical emergency like urinary obstruction. They are elective procedures intended to make genitalia look more typically male or female. Multiple human-rights bodies have called for their prohibition, and a systematic review of the medical literature found that the rationales offered for these surgeries are often not well supported by evidence, relying instead on parental preference and a desire for genital appearance that matches conventional expectations.15PubMed Central. Perspectives on conducting “sex-normalising” intersex surgeries conducted in infancy: A systematic review
The core ethical argument against early surgery is simple: it is irreversible, it is performed on someone who cannot consent, and it may not align with the person’s eventual gender identity or preferences. Ethicists have argued that, except where there is a genuine medical necessity, surgery should be delayed until the individual can decide for themselves.16BMC Medical Ethics. A principled ethical approach to intersex paediatric surgeries Others in the medical community, including some families, argue that early intervention can reduce social stigma and simplify a child’s upbringing, though patient advocates point out that the long-term evidence for psychological benefit is weak. An ethical framework developed for the medical management of DSD in children and adolescents acknowledges this tension, noting that some advocacy groups have called for a full moratorium on feminizing or masculinizing operations before the age of consent unless a medical emergency demands it.17PubMed Central. Ethical principles and recommendations for the medical management of differences of sex development (DSD)/intersex in children and adolescents
Sex Verification in Sports
The terminology debate has also played out in athletics, where intersex bodies have collided with sport’s insistence on a clean male/female binary. International sports organizations have used various forms of sex testing since the 1930s, relying on shifting scientific criteria to determine who qualifies to compete in women’s events.18PubMed Central. Testing sex and gender in sports; reinventing, reimagining and reconstructing histories The methods have changed over the decades, from physical inspections to chromosomal tests to testosterone thresholds, but the underlying assumption has stayed the same: that sex is a reliable binary category with a clear dividing line.
Critical analyses of these policies have identified several contested assumptions at their foundation, including that sex functions as a clean binary, that sport is otherwise a level playing field, and that intersex athletes hold an inherent unfair advantage over non-intersex women.19PubMed. Policing the boundaries of sex: a critical examination of gender verification and the Caster Semenya controversy Each of these assumptions is more complicated than it appears. Biological advantages in sport come from many sources, including height, limb proportions, and cardiovascular capacity, most of which are not regulated. Singling out intersex variations for policing raises questions about whether the real concern is competitive fairness or gender normativity.
Legal Recognition and the “Third Sex” Question
A separate but related development has been the slow movement toward legal recognition of sex categories beyond male and female. Germany, for instance, has allowed a “diverse” (divers) sex marker on official documents since 2019, joining a small number of jurisdictions that have created formal space for people whose bodies do not fit a binary designation.20Studia Iuridica. Intersex newborns and people with nonbinary gender identity: The beginning of legal recognition In most countries, though, intersex people and nonbinary individuals remain in what legal scholars describe as a “legal limbo,” where the administrative system cannot accommodate their reality.
The legal question is distinct from the medical one. A person with an intersex condition may identify firmly as male or female and want their documents to reflect that. Others may feel that neither label fits. The push for a third option on birth certificates and identity documents is partly driven by intersex advocacy and partly by the broader movement for nonbinary gender recognition, though these are different populations with overlapping but not identical needs. The common thread is that systems designed around a strict binary create practical problems for people who do not fit it, whether the mismatch originates in their biology, their identity, or both.
How Biologists Use the Terms Now
In zoology and botany, “hermaphrodite” remains the standard and perfectly appropriate term. A garden snail is a hermaphrodite. An earthworm is a hermaphrodite. A clownfish that changes sex is a sequential hermaphrodite. The word carries no stigma in these contexts because it is biologically accurate: these organisms genuinely produce both types of gametes.
For humans and other gonochoristic species, biologists now use “intersex” to describe individuals with sex characteristics that do not clearly align with typical male or female categories.6Oxford Academic. Hermaphrodite, Gonochorist, and More: Navigating the Complexities of Sex-Related Language in Biology This is a cross-disciplinary convention, not just a medical one: evolutionary biologists studying sex-determination pathways, geneticists cataloging developmental variations, and clinicians diagnosing patients are all converging on language that keeps “hermaphrodite” in the nonhuman domain and uses more precise labels for human variation. The shift has not erased confusion. You will still find older textbooks, some legal codes, and plenty of informal conversation using the word for people. But in the scientific and medical literature published after 2006, “hermaphrodite” applied to a human is a dated usage that most professionals avoid.
Simultaneous hermaphrodites like the pond snail face their own resource trade-offs that have no parallel in human biology. Research on these organisms has explored how they balance investment in male function, female function, and growth, treating reproduction as a three-way allocation problem rather than a two-way one.21Biological Journal of the Linnean Society. Stress promotes changes in resource allocation to growth and reproduction in a simultaneous hermaphrodite with indeterminate growth This kind of question is fascinating from an evolutionary standpoint, but it underscores why “hermaphrodite” was never a useful description of humans with intersex traits: the biology it describes is genuinely alien to our species.