Sex Differences Above the Neck (TLDR: they are real & important) "We should let people be themselves, but in a world where both sexes have equal opportunities and where sex differences aren’t socially harmful. Given the copious data that [@SteveStuWill] presents, who can object to this path?"

From "Sex, Medicine and Moralization" in Perspectives in Biology and Medicine. By @byrne_a and me in special issue edited @jflier, out this month. "The dry scientific issue of the number and nature of the sexes was recast as a matter of justice, inclusion, validation, and harm prevention, with the outmoded binary position on the wrong side of history. The motives and character of those who defended the sex binary were—and still are—questioned by a prominent faction on the progressive left." Examples of moralization from, respectively, Scientific American, American Scientist, and The Lancet: "Given what we know about biology across animals and in humans, efforts to represent human sex as binary based solely on what gametes one produces are not about biology but are about trying to restrict who counts as a full human in society." (Fuentes 2023) "Worryingly, even within the sciences, the term biological sex has become a transphobic dog whistle. Whereas once some of us used this term to differentiate the biological factors we study from social or cultural ones, it has now been co-opted by those who insist on a sex binary and who deny the relevance or even reality of diverse bodies and of gender identities, roles, and expressions in humans." (Clancy et al. 2024: 81) "Although the gametic definition makes reference to biological systems, it is sophistry, not science. Those who promote this definition favour the assertion that sex inheres in gamete (sperm and egg) production because, in part, it facilitates their political aims by fueling unhinged panic in some quarters about transgender threats to traditional gender roles." (Richardson 2025, 436)

1/ A new article in @Ecology_Letters by a group of evolutionary biologists—pioneers and leading experts on the evolution of sex. (The article is open access, short, and clear.) "Biological sex is best defined as a binary classification of male and female reproductive strategies rooted in anisogamy, characterised by the production of two discrete gamete types of different sizes." "We call for a more differentiated discourse on sex, one that separates the scientific conception of biological sex from societal discussions regarding the diversity of gender expressions and identities in humans."