For a long time scientists have debated the timeline of the evolution of primates. The evolutionary history of both apes (hominoids) and old world monkeys (cercopithecoids), two predominant groups of primates, could only be traced back 20 million years through solid fossil proof. But scientists have hypothesized the divergence of the two groups occurred between 25 and 30 million years ago. Recent fossil evidence has begun to shine some light on the history of these animals.
The fossils were found in Tanzania in the Rukawa Rift, a western section of the larger East African Rift System. This area has a rich fossil record and also shows unique geographic circumstances because it is a divergent tectonic plate boundary. The physical geography, especially along this rift, is thought to influence the biology of the past and has helped steer the path of evolution.
A tooth belonging to the new species Nsungwepithecus gunnelli, the oldest known member of cercopithecoids; as well as a jawbone of new species Rukwapithecus fleaglei, an early member of the hominoids, were discovered. Both of these fossils help to refine the evolutionary timeline that led to the divergence of these groups and in turn help us better understand the origins of modern primates.
Nancy Stevens, an anthropologist at Ohio University and the lead author of the study in the journal Nature detailing these finds, remarked, “These finds can help us to further refine hypotheses about the timing of diversification of major primate groups.” The fossils provide examples of intermediary primates that occurred 25.2 million years ago. This confirms that the estimates regarding divergence made through molecular data were valid. Both these finds extend the fossil record of apes and old world monkeys into the Oligocene Epoch (34 to 23 million years ago).
Read the complete study from the journal Nature, published May 15, 2013.
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