Modern human societies demand enforcement of social and moral norms using two types of sanctions that have distinct historical origins. Informal sanctions (e.g., chiding a relative) have existed since the dawn of humanity, whereas formal sanctions (e.g., punishment by the state) emerged more recently—over the last few thousand years, when laws began to separate norm violations into illegal and non-illegal violations. However, little research has investigated the psychological mechanisms underlying people’s use of these two distinct systems of sanctions. We show for the first time that these different cultural histories have left detectable traces in people’s moral judgments of today. When considering formal sanctions, people are experts in discriminating among illegal violations of varying severity, which is an adaptation to the culturally recent introduction of authority and law. When considering light informal sanctions (e.g., disapproval), people are experts in discriminating among non-illegal violations of varying severity, which serves the regulation of countless social norms of modern times. Most strikingly, when considering heavy informal sanctions (e.g., lashing out), people show equal discrimination expertise for both illegal and non-illegal violations, which likely reflects the moral responses of ancient group living.