 The theory of evolution transforms the way we should understand the relationship between human organisms and the species to which they belong. The taxonomic assumption of TP5 was that species are individuated by means of intrinsic properties that are individually instantiated by certain organisms. Instantiating those properties is taken to be necessary and sufficient for those organisms to belong to the species. Evolutionary theory makes it clear that species, as population-level entities, cannot be individuated by means of the properties of lower-level constituents, in our case, of individual human organisms (Sober 1980: 355).