Christianity spreads fastest in smaller societies with political hierarchies, reports paper published online this week in Nature Human Behaviour.
Today, Christianity is the world’s largest religious family. However, it is unknown if its success is best explained by it being a grassroots movement with an empowering message for the downtrodden, or if missionary efforts to convert influential leaders - such as the famous conversion of the Roman Emperor Constantine - had a greater role.
Joseph Watts and colleagues analyse records on the conversion of 70 Austronesian island cultures between the 16th and 19th centuries to determine which factors are most strongly associated with the speed of adopting Christianity. The rich dataset and their methodology allowed them to compare conversion speeds between different island populations while controlling for potentially confounding factors like the travel time between islands and historical ties between island populations, such as a common cultural ancestry.
The authors find that stronger political leadership and smaller population size most strongly predicted rapid conversion times, whereas social inequality levels are not significantly associated with conversion speed. This suggests that Christianity did not spread in these populations because of its socially empowering doctrine, but because of the influence of leaders and how ideas spread faster in smaller populations.
In an accompanying News & Views article, Nicole Creanza notes that these findings have implications for understanding how culture evolves more generally, demonstrating how “knowing just a few population-level features, such as population size and political organization, substantially improves our chances of successfully predicting whether an idea will spread in a population”.