Researchers have studied the grisly practice of ritual human sacrifice in nearly 100 cultures - including pre-European New Zealand - and found it was widely used as a power play.
Researchers from the University of Auckland's School of Psychology, the Max Planck Institute for the Science of Human History in Germany and Victoria University wanted to test the link between human sacrifice and how unequal or hierarchical a culture was.
"Religion has traditionally been seen as a key driver of morality and co-operation, but our study finds religious rituals also had a more sinister role in the evolution of modern societies," said study lead author Joseph Watts.
The study, published today in leading journal Nature, analysed historical data from 93 "Austronesian" cultures.
Human sacrifice was widespread in Austronesia: 40 of the cultures in the study practised some form of it.