Humans, Dunbar found, are capable of maintaining significantly more social ties than the size of our brains alone could explain. He proved that each human is surprisingly consistent in the number of social ties we can maintain: About five with intimate friends, 50 with good friends, 150 with friends and 1,500 with people we could recognize by name. That discovery came to be known as “Dunbar’s number.”
And then Dunbar turned to figuring out why Dunbar’s number is so high. Did humor help us manage it? Exercise? Storytelling? That riddle has been Dunbar’s quest for years — and religion is the latest hypothesis he’s testing in his ongoing attempt to find the answer.

“Most of these things we’re looking at, you get in religion in one form or another,” he said.

Dunbar is just one of a recent wave of scientists who are interested in how religion came to be and how people have benefited from it. “For most of Western intellectual history since the Enlightenment, religion has been thought of as ignorant and strange and an aberration and something that gets in the way of reason,” said Christian Smith, a sociologist at the University of Notre Dame who studies religion. “In the last 10 or 20 years on many fronts, there’s been a change in thinking about religion, where a lot of neuroscientists have been saying religion is totally natural. It totally makes sense that we’re religious. Religion has served a lot of important functions in developing societies.”