LAUSANNE, SWITZERLAND—Evolutionary anthropologist Simon Powers and his colleague Laurent Lehmann of the University of Lausanne developed a computer model to study how small groups of egalitarian hunter-gatherers might have transformed into hierarchical cultures over the course of several generations. Archaeological evidence for this transition has been lacking. “We have good descriptions of ‘before’ and ‘after,’ but not anything during the actual transition,” Christopher Boehm of the University of Southern California commented in Science. The researchers found that groups made up of leaders and followers grew to about twice the size of the egalitarian groups, and that even when leaders took a large portion of the group’s surplus supplies, the followers received more than if they’d remained in a leaderless band, perhaps because leaders can organize large projects in an efficient manner. “What [Powers and Lehmann] have done here is take these ideas and make them work within a very elegant mathematical framework,” said Paul Hooper of Emory University.