Phrenology

Phrenology chart from 1880s

Phrenology was the study of the outside of the human head, its contours and bumps. The belief at the time was that a person's inner thoughts, feelings and proclivities could be determined, specifically a person's criminality or tendency toward evil behavior. It is today considered a pseudoscience. Some used it to justify evolutionary racism, Social Darwinism, and eugenics.