 Ambiguities about the definition of a unit of selection have also snarled the debate about selection processes at the species level. One response to the notion of species selection comes with a classic confusion: “It is individual selection discriminating against the individuals of the losing species that causes the extinction” (Mayr 1997: 2093). The individual death of species members is confused with extinction: “the actual selection takes place at the level of competing individuals of the two species” (Mayr 1997: 2093). Once we overcome such difficulties, and succeed in conceiving of species as unified interactors, we are still faced with two questions. The combining of the interactor question and the manifestor-of-adaptation question (in the engineering sense) led to the rejection of research aimed at considering the role of species as interactors, simpliciter, in evolution. Once it is understood that species-level interactors may or may not possess design-type adaptations, it becomes possible to distinguish two research questions: Do species function as interactors, playing an active and significant role in evolution by selection? And does the evolution of species-level interactors produce species-level engineering adaptations and, if so, how often?