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Palaeontological evidence for an Oligocene divergence between Old World monkeys and apes

2013; Nature Portfolio; Volume: 497; Issue: 7451 Linguagem: Inglês

10.1038/nature12161

1476-4687

Nancy J. Stevens, Erik R. Seiffert, Patrick M. O’Connor, Eric M. Roberts, Mark D. Schmitz, Cornélia Krause, Eric Gorscak, Sifa Ngasala, Tobin L. Hieronymus, Joseph Temu,

Amphibian and Reptile Biology

Molecular evidence suggests that the evolutionary split between hominoids and cercopithecoids occurred between 25 and 30 Myr ago, but fossil evidence for crown-group catarrhines (cercopithecoids and hominoids) before 20 Myr ago has been lacking; newly described fossils of a stem hominoid and a stem cercopithecoid precisely dated to 25.2 Myr ago help to fill this gap in the fossil record. Molecular evidence suggests that the evolutionary split between hominoids (apes and humans) and cercopithecoids (Old World monkeys) occurred between 25 million and 30 million years ago, but fossil evidence for the catarrhines (cercopithecoids and hominoids) only goes back some 20 million years. Nancy Stevens and colleagues go some way to filling this gap with the discovery of the earliest known evidence of both Old World monkeys and apes. The fossils, of a stem hominoid and a stem-cercopithecoid, were found in a stratum in the East African Rift of Tanzania precisely dated to 25.2 million years. This date, well back in the Oligocene epoch, adds greatly to the time in which both groups are known to have existed. Apes and Old World monkeys are prominent components of modern African and Asian ecosystems, yet the earliest phases of their evolutionary history have remained largely undocumented1. The absence of crown catarrhine fossils older than ∼20 million years (Myr) has stood in stark contrast to molecular divergence estimates of ∼25–30 Myr for the split between Cercopithecoidea (Old World monkeys) and Hominoidea (apes), implying long ghost lineages for both clades2,3,4. Here we describe the oldest known fossil ‘ape’, represented by a partial mandible preserving dental features that place it with ‘nyanzapithecine’ stem hominoids. Additionally, we report the oldest stem member of the Old World monkey clade, represented by a lower third molar. Both specimens were recovered from a precisely dated 25.2-Myr-old stratum in the Rukwa Rift, a segment of the western branch of the East African Rift in Tanzania. These finds extend the fossil record of apes and Old World monkeys well into the Oligocene epoch of Africa, suggesting a possible link between diversification of crown catarrhines and changes in the African landscape brought about by previously unrecognized tectonic activity5 in the East African rift system.