 Implicit in this discussion is the assumption that being a unit of selection at the group level requires two things: (1) having the group as an interactor, and (2) having a group-level engineering-type adaptation. That is, the approach taken combines two different questions, the interactor question and the manifestor-of-adaptation question, and calls this combined set the unit of selection question. These requirements for “group selection” make perfect sense given that the prime target was a view of group selection that incorporated this same two-pronged definition of a unit of selection (see Borrello 2010 for a philosophically-oriented history of Wynne-Edwards and his views on group selection).