It is currently believed that great apes, including humans, diverged from small-bodied apes roughly 17 million years ago, but analysis of a younger fossil that has features of both groups may reshape our understanding of this evolutionary path. Catarrhines are the group of primates that lived before Old World monkeys and apes diverged from each other, a split followed by further divergence among the Old World apes into small-bodied and greater apes. Some researchers believe that small-bodied apes are a dwarfed version of great apes, since this group lacks features found in catarrhines. However, the fossil of a small-bodied ape found in January 2011 in Catalonia, Spain, and named Pliobates catalonia, shares features of catarrhines and great apes, despite living roughly 11.6 million years ago, long after the two categories of apes were assumed to have diverged. For example, characteristic of catarrhines, the teeth are more primitive, with the sharp cusps more centrally located and prominent, yet its cranium and brain-to-body-mass ratio is more similar to that of a great ape. Perhaps the most intriguing aspects of Pliobates are its limbs, where pronation of the wrist allowed enough rotation for cautious climbing and clambering in trees, a trait of great apes, yet the elbow lacked a critical stabilization feature, used when hanging in trees, that differentiates living apes from other primates. To make matters even more perplexing, the external bony ear of Pliobates is more primitive than monkeys that lived before catarrhines. Collectively, these findings hint that the last common ancestor of all apes might have been less great ape-like than generally assumed. A Perspective by Brenda Benefit discusses this study in more detail, including the different evolutionary scenarios this new fossil could imply.
Article #8: "Miocene small-bodied ape from Eurasia sheds light on hominoid evolution," by D.M. Alba; S. Almécija; D. DeMiguel; J. Fortuny; M. Pérez de los Ríos; M. Pina; J.M. Robles; S. Moyà-Solà at Institut Català de Paleontologia Miquel Crusafont in Barcelona, Spain; S. Almécija at George Washington University in Washington, DC; J.M. Robles at FOSSILIA Serveis Paleontològics i Geològics in Barcelona, Spain.