Humans are funny creatures. I am forever marveling over how the mind of our species has evolved and how it thinks.
This guy, Joe Henrich, is an evolutionary anthropologist in British Columbia, Canada. He wrote a paper about how religions owe their success to their martyrs, which I found on New Scientist.
According to Mr. Henrich, if a religious leader is willing to sacrifice himself in a costly manner for his belief, this gives him credibility and helps that belief spread. If no one is willing to make a significant sacrifice for a belief, even young children will pick up on this and withhold their own commitment.
The more costly the behavior, the more likely it is to be sincere. If someone is willing to give their life, then it is for an ideal they believe in. This is even more important if the martyr is a high-status priest or leader.
Then, once people believe, they are more likely to perform similar displays themselves, such as vows of chastity or poverty. Henrich created a mathematical model to test this self-enforcing loop that can stabilize and help a system of beliefs persist over time.
This explains why religions have such costly renunciations. For example, the Romans persecuting the early christians actually may have led to the spread of those beliefs be letting their early believers to be martyrs. It is an ultimate credibility-enhancing display.
This is also shown in other social movements like utopian communes like the Shakers and the Hittites. The stricter the demands on their followers, the more likely the system would persist. Henrich says, "You can see the changes in action. The number of those costly commitment rituals increases over time."
This is still a hypothesis, and needs to be tested. But it sure does seem to explain things. If Henrich is right, then it explains why evangelical churches in the US are increasing in number, while it would predict that more liberal, less demanding churches would lose their flock because it would reduce their followers' commitment.
Henrich says, "To be a member you've got to walk the walk and talk the talk. And this transmits deeper faith to the children."
Personally this seems disturbing and macabre but it does explain a phenomenon that has baffled me in regards to religions. This is definitely an area of research that I'd like to see developed.
Here is the pdf of the paper: The evolution of costly displays, cooperation, and religion. Inferentially potent displays and their implications for cultural evolution. By Joseph Henrich