Adaptation, Multilevel Selection, and Organismality: A Clash of Perspectives

The transitions revolution has transformed the levels of selection debate. My question is: How does acceptance of multilevel selection oblige us to revise our ideas about adaptation? In order to extend the concept of adaptation to a hierarchical setting, we must relax the assumption that adaptations occur only at one fi xed hierarchical level and determine whether they can be borne by the units at higher and lower compositional levels. I call this an additional dimension to the problem of adaptation because as well as settling the question whether selection is behind the emergence of some trait, as opposed to something like constraint, we are forced additionally to determine the hierarchical level at which selection is acting.