Does Everything Have to be a Species?

Evolution determines ancestry by reference to a phylogenetic tree. Phylogenetic trees are built based on homologous traits. Homology refers to similarity in the traits. Therefore, in the evolutionary view, gross overall similarity, in either genetics or morphology, is determining ancestry. This idea matters for our discussion because speciation, in an ultimate sense, is a question of ancestry. Many species concepts appeal in some sense or another to a most recent common ancestor.

Darwin's Finches

Essential Nature Baraminology

The argument presented by Joubert is fairly straightforward. He argues that the original kinds possessed what he called an “essential nature”. This nature is built into the original kinds, and was the force that held the various characteristics of the kind together into a coherent whole. He further argues that, since the nature was built into the kinds from the beginning, it has not changed. Therefore, we should be able to determine kinds by looking at their essential natures.