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Scientists have discovered the first gibbon fossil

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Hylobatidae – a family of monkeys that includes 20 species of living gibbons, are found throughout tropical Asia, from northeast India to Indonesia. The fossil record of hylobatids is poorly known. Most specimens are isolated teeth and fragmentary jaw bones found in caves in southern China and Southeast Asia dating no more than 2 million years ago.

Recently, a discovery by a team of scientists could fill a gap in the evolutionary history of apes. New York University scientists have discovered the oldest gibbon fossil in the Yuanmou region of Yunnan province in southwest China. The fossil is that of a small monkey called Yuanmoupithecus xiaoyuan.

The study mainly focused on teeth and cranial specimens of Yuanmoupithecus, which included an upper jaw from an infant under 2 years old at the time of its death. Using molar size as a guide, scientists estimate that Yuanmoupithecus was similar in size to today’s gibbons, with a body weight of around 6 kilograms, or about 13 pounds.

Terry Harrison, professor of anthropology at New York University and one of the authors of the article, said: “This new discovery extends the fossil record of Hylobatidae to 7-8 million years ago and, more specifically, improves our understanding of the evolution of this family of apes.”

“The teeth and underside of Yuanmoupithecus are very similar to those of modern gibbons, but in a few features the fossil species was more primitive and indicates that it is the ancestor of all living species.”

Xueping Ji of the Kunming Institute of Zoology and lead author of the study discovered the infant’s upper jaw during his field investigation. He identified it as a hylobatid by comparing it to modern gibbon skulls at the Kunming Institute of Zoology. He invited Harrison and other colleagues to work on specimens amassed over 30 years and held at the Yuanmou Man Museum and the Yunnan Institute of Cultural Relics and Archeology in 2018.

Harrison said, “Remains of Yuanmoupithecus are rare, but with diligence it was possible to recover enough specimens to establish that the fossil monkey Yuanmou is indeed a close relative of living hylobatids.”

The study also reported that Kapi ramnagarensis, which was claimed to be an earlier species of hylobatid based on a single isolated fossil molar from India, is not a hylobatid after all, but a member of a more primitive group. of primates that are not closely related. modern day monkeys.

Harrison warns, “Genetic studies indicate that hylobatids diverged from the lineage leading to great apes and humans around 17 to 22 million years ago, so there is still a 10 million year gap in the fossil record that must be filled. With continued exploration of promising fossil sites in China and elsewhere in Asia, it is hoped that additional discoveries will help fill these critical gaps in the evolutionary history of hylobatids.

Journal reference:

  1. Xueping Ji et al. The oldest hylobatid from the Upper Miocene of China. Journal of Human Evolution. DOI: 10.1016/j.jhevol.2022.103251