A Note Against the Use of "Belonging To" Properties in Multilevel Selection Theory

In this short paper, I argue against what I call the "belonging to" interpretation of group selection in scenarios in which a group's fitness is defined as the per capita reproductive output of the individuals of the group. According to this interpretation, group selection acts on "belonging to" properties of individuals, i.e. on relational or contextual properties that all the individuals of a group share simply by belonging to that group; thus, if differences in the individuals' "belonging to" properties cause differences in their fitness, group selection sensu the "belonging to" interpretation is said to be at work. I argue that the main problem with the "belonging to" interpretation is that it confuses evolutionary changes due to differences in environmental quality with evolutionary changes due to selection. In other words, I argue that, in the majority of cases, this interpretation actually takes the "selection" out of the "group selection" notion it aims to interpret: by adopting this perspective, one implicitly commits to explaining the evolutionary change under consideration not by a kind of selection (be it individual or group selection), but by differences in the environmental quality experienced by individual types.