If criminal behavior were merely a choice, the crime rates would more likely be evenly spread. However, when European researchers started to calculate crime rates in the 19th century, some places consistently had more crime from year to year. These results would indicate criminal behavior must be influenced by something other than choice and crime, and must be correlated with other factors.

Positivism is the use of empirical evidence through scientific inquiry to improve society. Ultimately, positivist criminology sought to identify other causes of criminal behavior beyond choice. The basic premises of positivism are measurement, objectivity, and causality.^[1] Early positivist theories speculated that there were criminals and non-criminals. Thus, we have to identify what causes criminals.

Charles Darwin wrote On the Origin of Species (1859), which outlined his observations of natural selection.^[2] A few years later, he applied his observations to humans in Descent of Man (1871), whereby he claimed that some people might be evolutionary reversions to an early stage of man.^[3] Although he never wrote about criminal behavior, others borrowed Darwin’s ideas and applied them to crime.