Amino Acid Sequence Evidence on the Phylogeny of Primates and Other Eutherians

Abstract

The biomolecular approach to systematic and evolutionary biology is in a state of transition. Laboratories that had been determining the amino acid sequences of proteins are now caught up by the excitement of the new recombinant DNA gene cloning and sequencing technology. The possibilities for advancing knowledge in systematic and evolutionary biology by application of this new technology seem almost boundless. It is obvious that knowing the actual nucleotide sequences of genes, rather than having to infer them from the amino acid sequences of encoded proteins, allows more accurate data to be used in figuring out the genealogic relationships of organisms (see Hewett-Emmett et al., this volume, Chapter 9; also Scott and Smith, this volume, Chapter 8). During the transition, while laboratories engaged in studying molecular evolution are retooling in order to engage in nucleotide sequencing, it is worth preparing for the impending flood of these gene sequence data by taking stock of what has already been learned about phylogeny from the substantial body of amino acid sequence data. With that objective in mind, this chapter focuses attention on the phylogeny of the order Primates, both on the subbranching within the order and on the genealogic position of Primates within the subclass Eutheria as well as on the broader pattern of vertebrate branching. We will concentrate on these groups because more species are represented in them by amino acid sequence data than in any other eukaryotic branch.