Suffering for your beliefs makes others believe too..

What is the difference between Jesus Christ and Superman? The content of religions and popular tales is often similar, but only religions have matyrs, according to an analysis of behavioural evolution published this week.

When religious leaders make costly sacrifices for their beliefs, the argument goes, these acts add credibility to their professions of faith and help thier beliefs to spread. If, on the other hand, no one is willing to make a significant sacrifice for a belief then observers - even young children - quickly pick up on this and withhold their own committment. The more costly the behaviour, the more likely it is to be sincere: few would willingly give their life for an ideal they did not belive in, and devotees who take vows of poverty or chastity are clearly putting their money where their mouth is. Such credibility enhancing displays are even more effective if performed by a high status individual such as a priest or other leader. Once people believe, they are more likely to perform similar displays themselves.

Joseph Henrich an evolutionary anthropologist at the University of British Columbia in Vancouver, Canada created a mathematical model to test these ideas and showed that this self-reinforcing loop can stabilise a system of beliefs and actions, and help them persist through many generations. This dynamic helps explain why so many religions involve costly renunciations.

For example, Henrich notes that the persecution of early Christians by Roman authorities may have spread Christian beliefs by allowing believers to be matyred for their faith - the ultimate credibility-enhancing display. The principle applies to other social movements too. Studies of 19th century utopian communes such as Hutterites and Shakers show that those making the strictest demands on their followers were most likely to persist. You can see the changes in action. The number of those costly committment rituals increases over time.

Henrich's analysis fills an important hole in our understanding of the rise of religions, says Richard Sosis, an anthropologist at the university of Conneticut in Storrs. The hypothesis still needs to be tested, for example with lab experiments on belief transmission, and historical studies of religions. But if Henrich is right, churches that liberalise their behavioural codes may be sabotaging themselves by reducing their followers committment. This may explain why strict evangelical Christian churches are expanding in the US at the expense of mainstream denominations. "To be a member you've got to walk the walk and talk the talk," says Henrich. "And this transmits deeper faith to the children."

New Scientist

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