Researchers from the University of Auckland and Victoria University of Wellington set out to answer the question and they arrive at a rather disturbing conclusion. The study, published in Nature (pdf), suggests that human sacrifice helped drive the transition from small, more equal societies to the larger, stratified ones we live in today.

This isn’t an entirely new idea. Social scientists and biologist have long debated the hypothesis that human sacrifice legitimizes class-based power distinctions seen in stratified societies, as it combines the display of ultimate power—taking a human life—with supernatural justifications that sanctify authority. Now, researchers were able to use sophisticated statistical modeling to put this hypothesis to the test.

They studied 93 traditional Austronesian societies, which contain various groups of people who share a family of language. Austronesians, who originate from Taiwan, eventually spread to Madagascar, Rapa Nui, and New Zealand.

Researchers write that they chose to analyze Austronesian societies because of their diversity:

They inhabit environments ranging from tiny atolls to continents, and their social structures ranged from small egalitarian, kin-based societies such as the Dobuans, to large, complex polities such the Hawaiians

For each society, researchers noted the presence or absence of human sacrifice and then coded the level of social stratification in the society into three levels; “egalitarian” (ones where wealth and status was not inherited), “moderately stratified” (there were inherited differences), or “highly stratified” (where there was little possibility of social mobility).

They found the extent of social stratification and presence of human sacrifice differed throughout the different societies. Human sacrifice was observed in 40 of the 93 cultures analyzed—five out of 20 egalitarian societies, 17 out of 46 moderately stratified societies, and 18 out of 27 highly stratified societies.

Researchers created family trees, based on how languages evolved between these societies, to see how Austronesian cultures were related to each other and how they evolved. They then used statistical models to test the effect of human sacrifice on how societies evolved. They were looking to see whether there was a link between ritual killings and high social stratification.

“Unpalatable as it might be, our results suggest that ritual killing helped humans transition from the small egalitarian groups of our ancestors, to the large stratified societies we live in today,” researchers note in the study.

That said, evolutionary anthropologist Joseph Henrich from Harvard University warns against seeing a causation between human sacrifice and modern, stratified societies. He told Science that he was skeptical of the researchers’ methodology of using the evolution of language to understand human behavior.

And yet, others welcome the use of statistical techniques. “The study of religion has been plagued in many ways by an abundance of ideas and a shortage of strong quantitative tests of these ideas,” behavior ecologist Richard Sosis of the University of Connecticut told Science.

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