Introduction

In the early twentieth century, eugenics emerged as a powerful scientific and political framework aimed at “improving” society by controlling reproduction and eliminating perceived difference. This module explores how these ideas reshaped understandings of gender diversity and contributed to the systematic targeting of trans and gender-nonconforming people.

Building on earlier Victorian scientific thinking, eugenics reframed gender nonconformity not simply as immoral, but as a biological and social threat to the nation. Within this framework, traits such as gender variance, sexuality, and non-normative behaviour were understood as hereditary, contagious, and dangerous to social stability.

These assumptions justified increasingly invasive forms of control. Medical and psychiatric systems classified trans and gender-diverse people in ways that made them visible to the state, enabling surveillance, institutionalisation, sterilisation, and other forms of coercion. Rather than neutral observation, science became a tool for defining who was considered “fit” to exist within society.

This period reached its most extreme expression during World War II, where Nazi persecution intensified existing eugenic ideologies rather than creating them. At the same time, the destruction of early research and archives on gender diversity created long-term gaps in knowledge that continue to shape public understanding and policy today.

Importantly, eugenics operated through intersecting systems of oppression. Trans and gender-nonconforming people were targeted not only for gender variance, but also through overlapping structures related to race, class, disability, and sexuality.

For activists, this history highlights how scientific authority can be mobilised to justify exclusion and control. It also reveals how narratives about biology, reproduction, and social order continue to echo in contemporary debates.

Understanding this legacy is essential for recognising when similar arguments reappear and helps provide a basis for challenging them before they become embedded in policy, law, or public belief.