 At the birth of the “interactor” concept, the concept of “evolvers” was also introduced, which are the entities that evolve as a result of selection on interactors: these are usually called lineages (Hull 1980). So far, no one has directly claimed that evolvers are units of selection. They can be seen, however, to be playing a role in considering the question of who owns an adaptation and who benefits from evolution by selection, which we will consider in sections  2.3  and  2.4.