分子證據(jù)表明,，人科動物（猿和人）與獼猴科動物（“舊世界”猴子）之間在演化上的分開發(fā)生在距今2500萬年和3000萬年之間,，但狹鼻猿（獼猴科和人科）的化石證據(jù)只追溯到大約2000萬年前,。Nancy Stevens及其同事發(fā)現(xiàn)了同時屬于“舊世界”猴子和猿的動物的最早已知證據(jù),，從而在一定程度上填補(bǔ)了這一空白,。他們所發(fā)現(xiàn)的化石是一種同時屬于處在進(jìn)化樹根部的人科動物和處在進(jìn)化樹根部的獼猴科動物的動物,，是在坦桑尼亞的東非大裂谷中的一個地層發(fā)現(xiàn)的,，其年代被精確測定為距今2520萬年前,。這個年代（屬于“漸新世”時期）大大延長了兩個類群的動物已知曾經(jīng)共存的時間范圍。（生物谷Bioon.com）
生物谷推薦英文摘要：
Nature doi:10.1038/nature12161
Palaeontological evidence for an Oligocene divergence between Old World monkeys and apes
Nancy J. Stevens, Erik R. Seiffert, Patrick M. O’Connor, Eric M. Roberts, Mark D. Schmitz, Cornelia Krause, Eric Gorscak, Sifa Ngasala, Tobin L. Hieronymus & Joseph Temu
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 undocumented. 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 clades. 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 activity in the East African rift system.
