To properly model all species with inheritence, species have to inherit from ancestors in the lineage. A Human IsA Primate because proto-primates evolved before

To properly model all species with inheritence, species have to inherit from ancestors in the lineage. A Human IsA Primate because proto-primates evolved before humans did. The hierarchy is a graph with a generation (time) axis. The dissonance comes in with timeless ontologies. Ontologies whose members don't share a common ancestor. Rather, the members share traits. Inheritance works in some cases, but not in all. Once it stops supporting all cases, it causes unnecessary complexity to the model.