Scott Alexander explores biological factors like lead exposure, omega-6 fatty acids, and lithium levels as potential explanations for historical crime rate trends, particularly the possible increase from 1850 to 1980. Longer summary

Scott Alexander discusses potential biological explanations for historical trends in crime rates. He provisionally accepts that crime may have increased from 1850 to 1980, contrary to his previous belief. He then explores three biological factors that could explain this trend: lead exposure, omega-6 fatty acid consumption, and lithium levels in water. Scott argues that increased lead exposure from industrialization, a dramatic rise in omega-6 fatty acid consumption, and decreased lithium in water due to modern purification methods could all contribute to higher crime rates. He presents evidence linking these factors to aggression and crime, including studies on dietary supplements reducing violence in various populations. Shorter summary