Levels and Hierarchies in Evolution

The concept of level of organization is a key component of our discussions of the nature of the biological world. I analyse the main characteristics of the hierarchy of levels of selection as manifestors of adaptation (which I equate to the hierarchy of levels of evolutionary organization) and show that, while ranked, the hierarchy of levels of selection is non-nested. Secondly, I consider a potential objection to my approach derived from Eronen and Ramsey’s (2022) claim that the notion of level of organization should be teased apart from the notion of level of selection, as they generate two distinct hierarchies. I argue that Eronen and Ramsey’s approach rests on a failure to distinguish between interactors and manifestors of adaptation, for while a hierarchy of interactors does not correspond to a hierarchy of levels of organization, a hierarchy of manifestors does.