Despite the recent advances in sequencing, bioinformatics, and phylogenetics there has been a lack of understanding and agreement about primate phylogeny. As a primate I find this wholly unacceptable. I should preface this discussion by saying I am not a primate biologist, nor do I have much understanding of deep mammal evolution or its controversies. As a molecular evolutionary biologist I do think it is amazing how detailed, and clarifying, an analysis can be with ample data. Perelman et. al. (2011) present a phylogeny of living Primates (Figures 1 & 2) that includes 90% of the known genera using 54 nuclear genes. Beyond the novel genetic information provided they have layered the available fossil information, and morphological, adapitive, bio-geographical, reproductive and behavioral traits that have been collected by countless scientists. It goes without saying (but I’ll say it anyway) this is an unbelievable amount of information!
Figure 1. Concatenated primate phylogeny representing 34,927 bp of genetic information from 191 taxa (186 primates). Coding and non-coding segments were selected from the X chromosome (4870 bp), Y chromosome (2630 bp) and autosomes (27,427 bp). Unmarked nodes have bootstrap values of 100%, while green dots represent <70%, grey 71-80%, black 81-90%, and red 91-99%.
Figure 2. Maximum likelihood tree of 186 primates from the same data as Figure 1. Numbers in boxes are divergence times of nodes in MYA. Smaller number represent nodes that are further described in Perelman et al. (2011).
The trees provides clear support for the Infraorder Lorisiformes, Lemuriformes, and Simiiformes, while placing the root of the primates on Dermoptera (Flying Lemurs). One of the major contributions of the above phylogeines is the clarification of sub0rder Strepsirrhini. This analysis provides clear support for a monophyletic origin the Strepsirrhini with a divergence from Haplorrhini 87 MYA. This is also the first analysis that clearly demonstrates the root of primates on Dermoptera. Dermoptera are, and have always been, exclusive to Asia indicating that Primates have a monophyletic origin from Asia 92 MYA. Finally, Perleman et al. (2011) show that Chiromyiformes and Lemuriformes are sister and have a monophyletic origin, proving a single colonization event on the island of Madagascar.
With this wide and diverse taxon sampling inferences on evolutionary rates can also be made. The global nucleotide substitution rates for the above taxa are 6.163 x 10-4 substitutions/site/MY. However, there is vast heterogeneity within specific lineages. The proposed “homonid-slow down” (~5.1 X 10-4 substitutions/site/MY) is no longer an exclusive event because Catarrhini also show a marked slow down (~4.8 X 10-4 substitutions/site/MY). Rate increases are also seen in Aotinae (7.2 X 10-4 substitutions/site/MY) where nocturnalism evolved ~8 MYA. These details layered upon existing knowledge make this a very impressive data set for the future study of human evolution.
Beyond the clarification of contentious or, previously, underrepresented taxa this study does more than provide pertinent information for primate biologists and primate evolution, it show us all the strength of molecular analysis in the context of ample biological data. This analysis sets a new benchmark for molecular taxonomic studies. As a species we are, obviously, interested in our own history and this study represents the culmination of all of that focused research. With a clarified understanding of our cousins and ancestors future applied research now has a genetic and taxonomic backbone to reference that will drastically aid in our ability to push the frontiers. As science and knowledge continue to expand with sequencing, ecological studies, and advancing methods we can only hope that other taxa can be as thoroughly understood as our own Order.
Perelman P, Johnson WE, Roos C, Seuánez HN, Horvath JE, Moreira MA, Kessing B, Pontius J, Roelke M, Rumpler Y, Schneider MP, Silva A, O’Brien SJ, & Pecon-Slattery J (2011). A molecular phylogeny of living primates. PLoS genetics, 7 (3) PMID: 21436896