How did William Harvey help change scientific understanding of malformations?

Before the 17th century, malformations were often attributed to supernatural causes, such as folklore or myths involving devils and monsters. William Harvey fundamentally shifted this perspective by initiating the objective study of these conditions.1

In 1651, Harvey correctly identified that malformations are not portents or supernatural events, but rather the result of deviations from the normal course of embryonic development. By framing these anomalies as biological processes rather than mystical occurrences, Harvey laid the conceptual groundwork for the scientific study of congenital disorders. While his work provided this essential shift in understanding, the systematic science of teratology was later formalized by French anatomists Étienne and Isidore Geoffroy Saint-Hilaire in the 19th century.1