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Christianity Spread Fastest in Small Politically Structured Societies

Over the past 2,000 years Christianity has grown from a tiny Judaic sect to the world’s largest religious family. Historians and social scientists have long debated whether Christianity spread through a top-down process driven by political leaders, or a bottom-up process that empowered social underclasses. In this study we collect historical data on 70 Austronesian cultures and test whether political hierarchy, social inequality, and population size predict the length of conversion times. We find that conversion to Christianity typically took less than 30 years and societies with political leaders and smaller populations were fastest to convert. In contrast, social inequality was not important, indicating that Christianity did not spread by empowered social underclasses. Our results show the importance of population size and structure in the cultural transmission of Christianity.

Read the full research article in Nature Human Behaviour, and a commentary by Dr. Nicole Creanza can be found here.

Human Sacrifice Facilitated Social Inequality

To mourn the death of aristocrats, the Ngaju people of Borneo performed a sacred ritual that began at sunset with the tying of a slave to a pole, involved dancing throughout the night and stabbing the victim, and then climaxed with the slave collapsing in a pool of his own blood at sunrise. In other parts of the world, methods of human sacrifice included bludgeoning, drowning, strangling, burning, decapitation, burial and even being used as the rollers to launch a newly built canoe. How could something as costly as human sacrifice have been so common in early societies? And why did these rituals need to be so dramatic and gory?

Read my summary article in Aeon here, the original article in Nature here, and F.A.Q. on human sacrifice here.

Pulotu, The Database of Pacific Religions


Austronesian speaking cultures are some of the greatest ocean voyagers in human history. From their homeland in Taiwan they settled as far west as Madagascar, as far east as Rapa Nui and as far south as New Zealand—a region spanning over half the world’s longitude and over a third of its latitude. The population sizes of traditional Austronesian cultures ranged from the low hundreds up to the hundred of thousands and they developed a wide range of subsistence technologies, social structures and religious systems. I led a team of researchers to build a freely available database of Austronesian cultures named Pulotu, meaning “abode of the gods”. This database documents the traditional religious systems of 116 Austronesian cultures and includes information on their social structures and physical environments.

The database can be freely viewed here, and you will find a paper describing how and why the database was built here.

Big Gods and Big Societies


Over half of the world’s population currently follow one of two closely related religions, Christianity and Islam. The concept of a Big God, who actively monitors human behaviour and punishes immoral actions, is a major feature of these religions and has been suggested to help build large complex societies.

I discuss the role of Big Gods and supernatural punishment in human prehistory here, and my cross-cultural research on supernatural punishment in traditional cultures can be found here.