Biological and social materiality

Workers’ Liberty supports trans and gender-diverse (TGD) people's rights. Some left feminists see those as threatening women’s “sex-based” rights. This article is part of a series which attempts to thread a path for left-wing activists to reach more agreement.

Here I examine biological and social materiality. Following articles will look at debates around toilets and change rooms, sport, prisons, and a summary about socialist attitudes.

I use “assigned sex at birth” for biological sex, and “gender identity” for psychological and social identification. I am a university and gender-affirming health clinic researcher. I identify as a gender-non-conforming man (he/they). Nothing I write here represents my employers’ stance.

A key argument by many sex-based rights activists (SBRAs) is that biological sex is real and material, but gender identity is “just a social construct”, or a construct of individual fantasy. Kathleen Stock calls gender transitions "immersive fictions", though she says others should respect those fictions, for example by using preferred pronouns. This argument, I believe, ignores the materiality of social constructs: essentially everything that oppresses us is a social construct – capitalism, the state, nationalism, colonialism, sexism, racism, ableism, homophobia, transphobia etc. It also underestimates the complexity of biological "materiality".

And all human gains are also through social constructs. Medicines and health systems are social constructs that change human biology. For example, conditions that prevented people from giving birth are now overcome through developments like in-vitro fertilisation. The SBRA position often falls backs to biological determinism about women’s social position. This provides the philosophical basis for the alliances which many SBRAs make with right wing patriarchal forces.

By contrast, Simone de Beauvoir famously argued that “One is not born, but becomes a woman”; that biological differences are transformed into social norms of what it is to be a woman or a man. Those norms shape what gender identity positions and gendered social behaviours are culturally intelligible in any particular place and time.

Having a gender identity that differs from that assigned at birth is not the same as digressing from gender roles and stereotypes. Despite current anti-trans backlashes, it is more widely accepted than in past decades that girls and women can be "tomboys" or "butch", and boys and men can be "effeminate". It is a distinct fact that throughout human history a minority of people have a deeply-felt, stable, gender identity which does not "match" sex assigned at birth.

There is great variability in gendering across languages. In French or Russian every noun is gendered. In Germany, children must by law have a gendered first name aligned with their sex assigned at birth. In Finnish, by contrast, there are no male and female pronouns. All pronouns are non-gendered. Refusal to use female pronouns for trans women aligns with gendered rules of language that are a historical product of patriarchy.

The etymology of “woman” is from “wifman” meaning wife of man. From 1975, that led many of the SBRAs’ predecessors to reject the term and use “womyn” or “wimmin”. In 1991, the Michigan Womyn's Music Festival decided to exclude trans women, accepting only "womyn-born-womyn" - a term which specifically excluded trans women.

There obviously are biological sex differences, but not so neatly that everyone is "obviously" and "immutably" male or female, with no grey areas. From a strictly genetic viewpoint, sex is a matter of small and large gamete producers. However, a significant minority of humans produce no gametes at any time of their lives. Some people with XY chromosomes and intersex conditions will through their whole lives "appear" to themselves and everyone else as unquestionably female but have not ovaries, instead undeveloped testes.

Hormone levels and their effects on secondary sexual characteristics (e.g. body fat distribution, hair growth, muscle mass development, breast size), vary greatly within sexes and between ethnicities and other human variation. For example, birth assigned women from some ethnicities may have more body hair on average than birth assigned men from other ethnicities. Poly-cystic ovarian syndrome, and many other hormonal variations, give individuals visible biological traits varying from their birth-sex norm.

Capacity, and actuality, of bearing children is the key biological issue within patriarchal attitudes – the basis for prescribing social roles around bearing and raising children, and limiting women’s activities. Many people cannot produce viable gametes. Historically, people assigned female at birth who could not, or chose not to, bear children were often excluded from the main category woman – instead being described as “maidens” or “barren women” or other terms.

Some intersex conditions mean people’s external genitals differ from those usually aligned with their internal gonads. Until recently it was routine to assign male or female sex to these infants and operate to “correct” their genitals. Surely, operating on intersex children to align their body with a presumed gender identity is inappropriate until they are capable to be fully involved in that decision.

There are some parallels between intersex and TGD people, though intersex activists stress these should not be over-emphasised. Medically-transitioned TGD people have many biological sex "markers" changed.. When trans people have gender affirming hormones or surgery, the results are major biological changes to their bodies. Trans women on estrogen have breast growth, redistribution of body fat, loss of muscle mass, reduction of scalp hair loss and other changes that are using seen as feminising. Trans women on testosterone experience redistribution of body fat, muscle growth, facial hair growth, and sometimes increased scalp hair loss. Gender-affirming surgeries (previously called “sex-change” operations) align people’s genitals and/or chest/breasts with their gender identity.

Geneticists studying trans and intersex people describe complex interaction between genes, in-utero hormonal conditions, and in-utero and early life social influences. Some children with identical genetic intersex conditions, born by the same mother, end up with differently sexed bodies at birth. In short, there may well be some "biological" component to gender identity for trans and intersex people.

Homozygotic (identical genes) twins are much more likely to both be trans, than are heterozygotic (different genes) twins. A 2013 study on twins at least one of whom was transgender found 13 of 39 (33%) monozygotic pairs of assigned males and 8 of 35 (22.8%) pairs of assigned females were both trans. Among dizygotic pairs, only 1 of 38 (2.6%) pairs was both-trans. (Diamond 2013).

One recent review (Fernandez 2025) concludes: “A growing number of studies support the existence of biological underpinnings to the development and continuous distribution of gender identity, with evidence of genetic, epigenetic, hormonal, neuroanatomical and neurodevelopmental differences between groups of individuals that express different identities. However, these components contribute to, but do not determine, the final variance in gender identity, which is also influenced by multiple nongenetic factors, many of which are still unknown”. So it is not biological versus social causation, but a complex interaction.

Gender identity usually settles by around three years old, and many trans people have felt incongruity with ascribed gender since that age. Most people have a clearly male or female gender identityalthough with that some will have a consciously atypical gender expression. Others have a less binary gender identity, or may or may not conform to social expectations aligned with their sex assigned at birth.

We do not develop gender identity by being told we are male or female. In many societies (including ones with fierce gender stereotyping for adults) there is little or no gender stereotyping for toddlers. Nor do we do it by observing external physical differences between male and female, which at age three are small and rarely observed. Gender identity is not a fiction or fantasy, but a material part of human development. It usually correlates with sex observed at birth, but for a significant minority, it does not.