The basic problem in an evolutionary transition is how and under what conditions a group becomes a new kind of individual. Initially, group fitness is taken to be the average of the component lower level units, but as the evolutionary transition proceeds, group fitness becomes decoupled from the fitness of its members. Indeed, the essence of an evolutionary transition is that the lower level units must in some sense “relinquish” their “claim” to fitness, that is to flourish and multiply, in favor of the new higher level. This transfer of fitness from lower to higher levels occurs through the evolution of cooperation and conflict modifiers that restrict the opportunity for within group change and enhance the opportunity for between group change. Until eventually, the group becomes an evolutionary individual in the sense of having heritable variation in fitness at its level of organization and in the sense of being protected from the ravages of within group change by adaptations that restrict the opportunity for non-cooperative behaviors.
On the sociology side, this begs the question how robust specific aspects of human groups need to be in order to be well-interpreted as units of selection rather than sets of individuals.