Image: Tim Flach
As ever, it's not what you know, but who: the structure of social networks, both online and off, seems to confer leadership on those with the most friends. Chains of command can form without members of a group – including the leader – ever needing to know who's on top. It is often suggested that the most influential individuals are also the best connected, but the idea has been difficult to test in a real-world setting. Cedric Sueur of the Free University of Brussels (ULB), Belgium, and colleagues instead looked at how two species of macaque – Macaca tonkeana and Macaca mulatta – reach group decisions, such as when and where to move on. They found that the leadership hierarchy in both species emerged via a simple rule-of-thumb: individuals followed the lead of their closest affiliates. Consequently, the individual with the most social connections becomes the leader in a self-reinforcing hierarchy.