Stephen Stearns, teaching Yale's Evolution and Medicine course, asks a deceptively simple question: what counts as a patient once you factor in development. This short lecture, drawn from the textbook Evolutionary Medicine (Sinauer Associates, 2015), lays out the developmental origins of health and disease framework, the idea that conditions experienced in the womb and early infancy can set an individual's later susceptibility to illnesses like diabetes, heart disease, and obesity. Stearns walks through how fetal programming and developmental plasticity mean that a person's health trajectory is shaped well before symptoms appear, complicating the standard clinical picture of a patient as someone who simply presents with disease. The lecture sits within a broader series applying evolutionary biology to medical practice, treating this concept as a bridge between developmental biology and clinical diagnosis.