A team of researchers has discovered the earliest fossilized gibbon, filling a gap in the primates' evolutionary history. The fossil was found in southwest China's Yunnan Province's Yuanmou region. 

(Photo : James St. John/Wikimedia Commons)
Fossil shark teeth and fish bones

Fossilized Gibbon Yuanmoupithecus Xiaoyuan from the Hylobatid Ape Family

According to New York University, the small ape found in China is called Yuanmoupithecus xiaoyuan, which belongs to the hylobatid family. It was close in size to modern-day gibbons, with a body weight of roughly six kilograms, or about 13 pounds, based on the size of the molar teeth.

The hylobatid ape family has 20 species of living gibbons, and they can be found from northeastern India to Indonesia in tropical Asia.

According to Terry Harrison, an anthropology professor at New York University and one of the paper's authors, fossilized hylobatid fossils are extremely uncommon. The majority of the fossils, he continued, are isolated teeth and broken jaw bones discovered in caves in southern China and Southeast Asia that are no older than two million years.

The latest discovery, according to the researcher, improves our knowledge of the evolution of this family of apes and pushes the fossil record of hylobatids back to seven to eight million years ago.

Although Yuanmoupithecus' teeth and lower face are remarkably similar to those of modern gibbons, the fossil species was more primitive in several areas, suggesting that it was the ancestor of all surviving species.

Hylobatid Research Details

During his fieldwork, Xueping discovered the infant's top jaw. By contrasting it with contemporary gibbon skulls kept at the Kunming Institute of Zoology, he was able to determine that it belonged to a hylobatid. He invited Harrison and other colleagues to work on specimens that were collected over a 30-year period and kept at the Yuanmou Man Museum and the Yunnan Institute of Cultural Relics and Archaeology in 2018.

Harrison issues a warning, noting that genetic research suggests the hylobatids split off from the lineage that produced humans and big apes between 17 and 22 million years ago. According to him, the fossil record still has a 10-million-year gap that needs to be filled. These crucial gaps in the evolutionary history of hylobatids are hoped to be filled by further research into promising fossil sites in China and other parts of Asia.

In order to conduct their research, the scientists also had access to skeletal and paleontological collections at a number of different institutions, including the National Museum of Natural History of the Smithsonian Institution in Washington, D.C., and the American Museum of Natural History in New York.

The research was released in the Journal of Human Evolution.

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Previous Study on Human Evolution

Dr. Mark Grabowski from the University of Tübingen's Senckenberg Centre for Human Evolution and Palaeoenvironment made significant advances in estimating the size and speculating on the lifestyle of the last ape and human ancestor in a 2017 study. 

Grawbowski and his team recreated body mass evolution during and before the human lineage using average and estimated body masses for a large sample of contemporary and fossil humans, apes, and other primates, as well as unique comparative methodologies.

The results of this study, published in Nature Communications journal, imply that the earliest apes likely lived in a habitat that supported gibbon-like size or an ape weighing around five kilograms. 

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