Forgive me for the semi automated point by point response to this letter but I am very tired:
This covers all of their points and how they are very very clearly wrong
They are trying to cloud the discussions with words they do not understand so everyone gets confused. This is what the Russians do in propaganda.
Sex is immutable and binary.
1. Claim: “Biological sex is not binary but bimodal”
Rebuttal:
This is a rhetorical sleight of hand. Biological sex is indeed binary, because it is rooted in the reproductive function of the organism: male and female, defined by the production of small or large gametes (sperm or ova). While there are rare disorders of sexual development (DSDs), these are precisely that—disorders, not third sexes. They do not invalidate the binary model any more than congenital limb deformities disprove that humans are bipedal. The attempt to redefine “sex” into a spectrum or modal distribution misrepresents the purpose of biological classification, which is functional and reproductive, not cosmetic or psychological.
2. Claim: “Sex is made up of a collection of traits that vary—chromosomes, hormones, etc.”
Rebuttal:
This mischaracterises how sex is determined. While multiple traits correlate with sex, they are not all equally defining. The determining factor of biological sex is chromosomal: XX = female, XY = male. Everything else (hormones, secondary sex characteristics) flows from this root. Medical interventions may modify appearance or hormone levels, but they do not change sex—they change presentation. To claim otherwise collapses the distinction between cause and effect.
3. Claim: “Anatomy is not fixed—surgery and hormones change sex characteristics, so sex is not immutable.”
Rebuttal:
This confuses phenotypic modification with change of sex. No surgery or hormone regime can produce fully functional reproductive anatomy of the opposite sex. A male who undergoes vaginoplasty does not acquire ovaries or the ability to gestate life. As the UK’s Gender Recognition Act recognises, legal sex may be changed, but biological sex remains immutable. The Forstater v CGD Europe judgment confirmed this view is protected under UK equality law.
4. Claim: “Medical transition causes profound biological changes that invalidate binary sex.”
Rebuttal:
Medical changes are real but limited in scope. Hormonal treatment affects blood chemistry and some physical traits, but this is not the same as changing one’s biological sex. Medicine routinely adjusts for patient context—e.g., using female ranges for post-menopausal women—but this does not alter their sex, merely recognises variability within sex. That’s standard clinical care, not a refutation of binary classification.
5. Claim: “Sex is only binary for reproduction, which is largely irrelevant to daily life.”
Rebuttal:
This dismisses the entire legal and social purpose of sex-based protections, especially for safeguarding. Biological sex matters profoundly in areas like single-sex spaces, sport, prisons, intimate care, and data collection. These are not hypothetical concerns—misclassifying biological males as females can have serious safety implications, particularly in women’s toilets, refuges, or hospital wards. Reducing sex to a reproductive detail is a dangerous abstraction.
6. Claim: “Simple models of sex lead to harm and should not guide policy.”
Rebuttal:
What leads to harm is policy made without regard for material reality or safeguarding duties. The Equality Act allows for single-sex exceptions precisely because binary sex distinctions matter in vulnerable contexts. The EHRC and Supreme Court have correctly affirmed that “biological sex” is the relevant category in law. That is not a political statement—it is a necessary legal and biological fact, and ignoring it risks undermining the rights of women and girls.
Final Thought
Science must be descriptive, not prescriptive. A great many of the signatories to this letter are researchers in psychology, gender studies, or public health—not evolutionary biology or reproductive medicine. That matters. The existence of complexity in sex development does not erase the fundamental binary nature of human sex. The law must protect all, including those with rare conditions—but it cannot be rewritten to appease belief systems that deny biological reality.