Wilson, D. S., Van Vugt, M., & O'Gorman, R. (2008). Multilevel selection theory and major evolutionary transitions: Implications for Psychological Science. Current Directions in Psychological Science, 17, 6-9 

Abstract:

The concept of a group as comparable to a single organism has had a long and turbulent history. Currently methodological individualism dominates in many areas of psychology and evolution, but natural selection is now known to operate at multiple levels of the biological hierarchy. When between-group selection dominates within-group selection, a major evolutionary transition occurs and the group becomes a new, higher-level organism. It is likely that human evolution represents a major transition, and this has wide-ranging implications for the psychological study of group behavior, cognition, and culture.