Baboon Comparative Genomics

By: Zachary Frament, Frederick Kalisz, Griffin Lyons, and Alexia Zambarano (Stonehill College, BIO323: Evolution, Spring 2019)

In this article, researchers wanted to conduct an extensive analysis of the evolutionary history of the genus Papio, the baboons, and its six species. The researchers wanted to explore the genetic relationships among the six extant species: Olive baboon (P. anubis), Yellow baboon (P. cynocephalus), Kinda baboon (P. kindae), Hamadryas baboon (P. hamadryas), Chacma baboon (P. ursinus), and Guinea baboon (P. papio). Each of the species differs morphologically and behaviorally, and they occupy completely different geographical areas in Africa. Although the ranges that the six different species reside in do not overlap, researchers were able to find that the baboon lineages were experiencing hybridization and interbreeding in recent and past times. Some of the ranges are particularly close to each other, nearly overlapping, yet these six different species do not resemble each other morphologically or behaviorally.

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Map of baboon species and table of their distinguishing features
Figure 1 from Rogers et al. (2019): “Papio baboon species. (A) The appearance and current distribution of each baboon species, and the locations of three well-documented active hybrid zones are also shown. x1: hybrid zone between P. hamadryas and P. anubis (19, 28), x2: hybrid zone between P. cynocephalus and P. anubis (17, 26), x3: hybrid zone between P. kindae and P. ursinus (18). Drawings of each species by S. Nash. (B) Distinguishing features of Papio species. Body mass data from (16, 59) and unpublished data from J.P.-C., J.R., and C.J.J.”

To conduct their research, the scientists sequenced and analyzed the species Papio anubis, or Olive baboons, and compared their genome to that of the other five species of baboons. From the whole genome sequencing of the Olive baboon and the other species, the researchers constructed phylogenies of the baboons to observe the differences and similarities among each species. The researchers focused some of their attention on the mitochondrial DNA of the baboons and created a phylogeny that represented seven different major haplogroups that disagreed with the phenotypic data. Through their insightful analyses of the phylogenies, the researchers found a common theme of Alu gene insertions throughout the genomes of the baboons. An increased rate of these insertions correlates with higher rates of hybridization in this research. Through statistical analyses and phylogenies, they found that hybridization was a common occurrence within the evolution of baboons. The hybridizations within the species led to introgressions, which are the transfer of genetic information from one species to another. Some lineages were impacted by admixture more, which led to more allele sharing between those species, but for the Chacma baboons and the Guinea baboons, there was less admixture. Chacma and Guinea baboons reside in different ranges that are far from each other, which can further explain that admixture would be less between them. From these findings, it clarifies that as lineages evolve, genetic material and information are exchanged between species, but they can still be very different phenotypically.

These research findings can show a helpful link to the possible admixture of other primate species such as humans, Neanderthals, and Denisovans. Although our genus Homo has evolved around the same period as Papio, our genus has only one species, whereas the baboons have gone through many speciation events. The study of captive baboons may also explain the complicated mechanisms of genetically predisposed complications in humans. This study has provided very significant data about the genus Papio, but due to their intricate genomic differences and novel insertions, more research needs to be done to try and gather more accurate information.

Citation: Rogers, J., M. Raveendran, R.A. Harris, T. Mailund, K. Leppälä, G. Athanasiadis, et al. 2019. The comparative genomics and complex population history of Papio baboons. Science Advances 5: eaau6947.

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