The science of the ‘third gender’: biological and social perspectives

The phrase “third gender” describes a social and legal category used in several societies for people whose gender does not fit the conventional categories of man and woman. It is often discussed alongside transgender identities, intersex variations, and long-established cultural communities such as hijras in South Asia. These terms overlap in public conversation, but they do not mean the same thing.

A scientific approach begins by separating sex from gender. Biological sex involves several characteristics, including chromosomes, reproductive anatomy, gonads, hormones, and secondary sexual traits. Gender refers to identity, social roles, expression, and the expectations attached to those roles. In real human lives, these dimensions can interact in complex ways.

Evidence-based discussion is especially important in India, where traditional communities, constitutional rights, medical care, and public policy meet. Respect for personal identity does not require abandoning scientific reasoning. It requires using accurate concepts, recognising variation, and avoiding claims that biology alone can define every person’s social identity.

Sex is a set of biological traits

Human biology is often presented as a simple male-female binary, but sex characteristics develop through several stages. Chromosomal patterns such as XX and XY are common, yet variations such as XXY, XO, mosaic patterns, and differences in sex development also occur. Gonadal tissue, internal reproductive organs, external anatomy, hormone production, and sensitivity to hormones may not align in the expected way.

These variations are commonly grouped under the term intersex, although people differ in whether they use that word for themselves. Intersex is not the same as being transgender or belonging to a culturally recognised third-gender group. It refers primarily to physical sex characteristics, while transgender and third-gender identities concern gender identity and social recognition.

No single biological test can classify every person’s gender. Chromosome testing, hormone analysis, or physical examination may provide information about sex characteristics, but they cannot determine a person’s identity, dignity, or social role.

Intersex variations show biological diversity

Intersex traits may be identified at birth, during puberty, when someone seeks fertility care, or through genetic testing. Some people have visible anatomical differences, while others have variations that are never medically detected. Examples include differences in androgen response, congenital adrenal hyperplasia, and variations involving sex chromosomes or gonadal development.

Medical treatment should focus on health, informed consent, and the person’s own needs. Historically, some children underwent irreversible procedures intended to make their bodies conform to conventional expectations, even when there was no immediate medical necessity. Current ethical debate increasingly emphasises delaying non-essential interventions until the individual can participate in the decision.

Recognising intersex diversity does not eliminate the usefulness of biological categories in medicine. Doctors still need detailed information about anatomy, hormones, genetics, and reproductive health. It does mean that healthcare must avoid assuming that every body follows one standard developmental pathway.

Gender identity develops through biology and society

Gender identity is a person’s enduring sense of being a man, a woman, both, neither, or another gender. Research suggests that identity is shaped by a combination of biological development, psychology, family life, culture, and personal experience. Scientists have not found a single “gender identity gene” or brain scan that can classify everyone.

Studies of transgender and gender-diverse people have examined genetics, prenatal hormone exposure, brain structure, mental health, and social development. Some findings suggest biological influences, but results are complex and cannot be used as a universal diagnostic test. Human behaviour rarely has one isolated cause.

A person’s gender expression may include clothing, voice, hairstyle, occupation, or mannerisms, but expression does not prove identity. Likewise, gender identity should not be treated as a psychiatric illness. Mental health difficulties often arise from stigma, family rejection, discrimination, and barriers to care rather than from gender diversity itself.

Indian traditions contain several gender categories

South Asia has long included communities whose identities and social roles do not fit a strict male-female framework. Hijra communities, for example, have histories involving ritual roles, kinship structures, performance, spiritual traditions, and distinct forms of community leadership. Terms such as kinnar and aravani are used in different regions, although their meanings and preferred usage vary.

These communities are not biologically uniform. Some members are transgender women, some are intersex, and others understand their identity through a culturally specific category. Treating every hijra person as having the same anatomy or life history creates scientific and social confusion.

India’s Supreme Court recognised the right of transgender people to identify as a “third gender” in the NALSA judgment of 2014. The Transgender Persons (Protection of Rights) Act, 2019, further addressed discrimination and legal recognition. Legal categories can protect rights, but they are administrative tools rather than complete descriptions of human biology.

Concept Primarily describes Possible examples What it does not automatically indicate
Biological sex characteristics Chromosomes, hormones, anatomy, and reproductive traits XX, XY, intersex variations A person’s gender identity
Intersex Variation in physical sex development Differences in gonads, anatomy, chromosomes, or hormone response A particular social identity
Gender identity A person’s internal sense of gender Woman, man, non-binary, hijra, transgender identity A specific chromosome pattern
Gender expression How identity or personality is presented socially Clothing, voice, behaviour, appearance Sexual orientation or anatomy
Third-gender category A cultural or legal status outside the conventional binary Hijra, kinnar, and other regional categories One universal biological condition

Language helps prevent scientific errors

Confusing sex, gender identity, sexual orientation, and gender expression leads to inaccurate conclusions. Sexual orientation concerns patterns of attraction; it does not determine whether someone is transgender, intersex, or third gender. Similarly, a person’s appearance cannot establish their chromosomes or anatomy.

Scientific communication should use the terms preferred by the people being described, while explaining distinctions clearly. Researchers should state how participants were classified, avoid treating small samples as universal evidence, and account for cultural differences. India’s gender-diverse communities cannot always be interpreted through categories developed in another country.

Public discussion should also avoid presenting traditional identities as superstition or, at the other extreme, romanticising them as untouched remnants of the past. Communities change over time, and their members may hold varied views about medicine, religion, family, employment, and legal recognition.

Building informed public understanding

Schools, media organisations, healthcare institutions, and public agencies can make discussions of sex and gender more accurate by combining biological literacy with respect for human rights. Useful practices include:

A rational society can recognise biological variation while accepting that social identities are shaped by culture, language, law, and personal experience. Read scientific sources critically, use precise language, and share evidence-based information that protects both accuracy and human dignity.