A new discovery fills a long missing gap in evolutionary history

baby upper jaw Yuanmobithex. Credit: Terry Harrison, NYU Department of Anthropology

The oldest gibbon fossil was discovered in southwestern China.

A team of researchers has found the oldest gibbon fossil, to fill a long-lost evolutionary gap in ape history.

The study published in Journal of Human Evolutionfocuses on the hylobatid family of monkeys, which includes 20 species of live gibbons that are found throughout tropical Asia from northeastern India to Indonesia.

“Fossil remains of heliopatids are very rare, and most specimens are isolated teeth and segmented jaw bones found at cave sites in southern China and Southeast Asia that date back no more than two million years,” explains Terry Harrison, a professor of anthropology in New York. University and one of the authors of the paper. “This new discovery extends the fossil record of heliotrope to 7 to 8 million years ago and, more specifically, advances our understanding of the evolution of this family of apes.”

The fossil, which was found in Yuanmou District, Yunnan Province in southwest China, is from a small monkey called Yuanmoupithecus xiaoyuan. Study analysis focused on dental and skull samples Yuanmobithexwhich included the upper jaw of a young child who was less than two years old at the time of his death.

Excavations near Leilao village in Yunnan

Excavations near Leilao village in Yunnan, one of the sites where Yuanmobithex Remains have been found. Credit: Terry Harrison, NYU Department of Anthropology

Using the molar size as a guide, Yuanmobithex Its size was close to the size of modern gibbons, with a body weight of about 6 kilograms – or about 13 pounds.

Teeth and down the face Yuanmobithex It is very similar to that of the modern-day gibbon, but in some features the fossil species was more primitive and indicates that it was the ancestor of all living species,” notes Harrison, who is part of the New York University Center for the Study of Human Origins.

Ji discovered the baby’s upper jaw during a field survey, and by comparing it to modern gibbon skulls preserved at the Kunming Institute of Zoology, he was able to identify it as a helioptide. In 2018, he invited Harrison and other colleagues to work on specimens collected over the past 30 years that have been at the Yunnan Institute of Cultural Relics and Archeology and the Yuanmou Man Museum.

“remains Yuanmobithex Extremely rare, but with diligence, it was possible to recover enough specimens to prove that the Yuanmu fossil monkey is indeed a close relative of living hylobatids,” notes Harrison.

The Journal of Human Evolution The study also found that Kabi Ramnagarensiswhich is claimed to be an earlier type of hylobatid, based on a single fossil molar isolated from India, is not a hylobatid after all, but a member of a more primitive group of primates not closely related to modern apes.

“Genetic studies indicate that hylobatids diverged from the lineage leading to apes and humans about 17 to 22 million years ago, so there is still a 10-million-year gap in the fossil record that must be filled,” warns Harrison. “With the ongoing 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 heliopauses.”

Reference: “The Oldest Heliopatids from Late Miocene China” by Xueping Jia, Terry Harrison, Yingqi Zhang, Yun Wub, Chunxia Zhang, Jinming Hui, Dongdong Wua, Yemao Hou, Song Li, Guofu Wang, Zhenzhen Wang, September 13, 2022 and Journal of Human Evolution.
DOI: 10.1016 / j.jhevol.2022.103251

The study was funded by the National Natural Science Foundation of China, the Yunnan Natural Science Foundation, and the Strategic Priority Research Program of the Chinese Academy of Sciences.

The researchers also gained access to skeletal and fossil collections at the American Museum of Natural History in New York and the Smithsonian’s National Museum of Natural History in Washington, D.C., among others, while conducting their study.

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