The neurodiversity movement has gained considerable momentum in recent years, asserting that conditions such as attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) represent natural variations in human neurodevelopment rather than pathological disorders (Baron-Cohen, 2017). This perspective has found increasing resonance among people with lived experience, advocacy groups and a growing number of clinicians. Yet, it has also attracted criticism for lacking a rigorous scientific foundation, leaving it vulnerable to the charge that it is more ideological than evidence based (Sonuga-Barke & Thapar, 2021). We argue that evolutionary psychiatry provides precisely the scientific framework that the neurodiversity movement needs. By asking why ADHD and ASD have persisted across human history, and answering through the mechanisms of natural selection, evolutionary theory transforms neurodiversity from an advocacy position into a scientifically grounded account of human variation.