It’s two years old, but Smithsonian has a nice interview with E.O.Wilson in which he speaks briefly about the group selection heresy. (Out-takes from that interview here).
The way I define it, group selection operates on the fitness, or lack thereof, of the social interactions in the group. In other words, it’s not simply group versus group in that sense but what actions individuals take that affect the group. And that would of course be communication, division of labor and the ability to read others’ intentions, which leads to cooperation.
When it’s an advantage to communicate or cooperate, those genes that promote it are going to be favored in that group if the group is competing with other groups. It gives them superiority over other groups and the selection proceeds at the group level, even as it continues to proceed at the individual level.
I usually give a simplified version of group selection – “the largest group of mutual altruists always wins” – but people generally don’t understand my point. Wilson, unsurprisingly, has a cleaner explanation.
Within groups, selfish individuals win and between groups, altruistic groups beat groups of selfish individuals.