How did William Harvey explain the origin of malformations in 1651?

In 1651, the English physiologist William Harvey initiated the objective study of malformations by correctly attributing them to deviations from the normal course of embryonic development.1

Prior to this scientific shift, many cultures attributed such abnormalities to supernatural causes, often incorrectly linking them to myths or interactions between humans and devils or animals. By identifying that these structural anomalies were rooted in the biological processes of development rather than folklore, Harvey laid the groundwork for the future science of teratology.12