Originating in the late 19th century and early 20th century with the ideas of Cesare Lombroso and Earnest Hooton, researchers have long taken an interest in understanding violent behaviors in terms of biological factors. These early works had racist overtones and were used to inform some unfortunate policies, including eugenics and euthanasia. Following the fallout from these movements, researchers began to distance themselves from exploring the biological correlates of aggression and instead focused on environmental influences. In the past several decades, however, literature again has begun to showcase studies that provide support for biological risk factors. Because the growing empirical evidence is assumedly free of political agenda and consistently demonstrates support for biological predictors of aggression, biological criminology has reappeared, and the field is growing.

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