Gamete Size Defines Two Biological Sexes, According to New Study Promoted by SEGM

A recent study, highlighted by the Society for Evidence-Based Gender Medicine (SEGM) and evolutionary biologist Colin Wright, asserts that biological sex is fundamentally determined by gamete size, concluding that there are only two sexes: male and female. The announcement, made via SEGM's social media, directly quotes Wright's interpretation of the findings.

The tweet, posted by SEGM, stated, "> A new study about sex concludes that size matters. The size of gametes, that is. “Male” organisms' biological function is to produce small gametes (sperm), and “female” organisms's function is to produce large gametes (ova). There are only 2 sexes, concludes @SwipeWright." This statement underscores a biological principle known as anisogamy, where the distinction between sexes is based on the production of small (sperm) or large (ova) gametes.

Colin Wright, an evolutionary biologist and fellow at the Manhattan Institute, has consistently articulated views aligning with this definition of biological sex. His public commentary often centers on biological distinctions, and he is a contributing editor for platforms like Quillette. SEGM, a non-profit organization founded in 2019, advocates for evidence-based practices in youth gender medicine and frequently challenges the scientific basis of gender-affirming care.

The concept of anisogamy is a foundational principle in evolutionary biology, describing the differentiation of gametes into two distinct sizes. This biological reality underpins sexual reproduction in many species, including humans. The study referenced by SEGM and Wright appears to reinforce this established biological framework in the ongoing public discourse surrounding sex and gender.