"The Hutterites (who came out of the same tradition as the Amish and the Mennonites) have a strict policy that every time a colony approaches 150, they split it in two and start a new one. "Keeping things under 150 just seems to be the best and most efficient way to manage a group of people," Spokane told me. "When things get larger than that, people become strangers to one another." The Hutterites, obviously, didn't get this idea from contemporary evolutionary psychology. They've been following the 150 rule for centuries. But their rationale fits perfectly with Dunbar's theories. At 150, the Hutterites believe, something happens-something indefinable but very real-that somehow changes the nature of community overnight. "In smaller groups people are a lot closer. They're knit together, which is very important if you want to be be effective and successful at community life," Gross said. "If you get too large, you don't have enough work in common. You don't have enough things in common, and then you start to become strangers and that close-knit fellowship starts to get lost." Gross spoke from experience. He had been in Hutterite colonies that had come near to that magic number and seen firsthand how things had changed. "What happens when you get that big is that the group starts, just on its own, to form a sort of clan." He made a gesture with his hands, as if to demonstrate division. "You get two or three groups within the larger group. That is something you really try to prevent, and when it happens it is a good time to branch out."