Brain traits through phylogeny: evolution of neural characters.

We have previously derived a hypothetical tree of the lines of mammalian descent, based upon a comprehensive numerical taxonomic cross-analysis of primitive and derived states of 15 brain traits in 38 representative species. In this communication we use this tree to describe the probable sequence of changes that have taken place in phylogenetic history. 2 characters proved to be multiply convergent, occurring in parallel in several disparate lines of descent. The remaining 9 characters each appeared in ancestors of one or another of the lineages and characterize related progeny.