Thanks to Russell for the following:

http://phys.org/news/2012-07-herding-sheep-selfish.html

Emotion is a calculus of motion, feelings are the capacity to apprehend the midpoint of a flow system. Calculating the motion of individual prey animals renders the center mass of the herd and/or defensive formation. The midpoint is place of maximum vulnerability, thus, the young are concentrated at the center. Orbiting the midpoint of the flow system, is the first step to becoming entrained within that flow system. Hunting evolves into herding.