Paleontologists have found the remains of Mesopithecus pentelicus — an extinct species of Old World monkey that lived in Europe and Asia between 7 and 5 million years ago — in the Shuitangba lignite mine in northeastern Yunnan Province, China. The discovery indicates that this monkey species existed in Asia at the same time as apes, and is probably the ancestor of some of the modern monkeys in the area.
“This is significant because they are some of the very oldest fossils of monkeys outside of Africa,” said Professor Nina Jablonski, an anthropologist in the Department of Anthropology at the Pennsylvania State University.
“It is close to or actually the ancestor of many of the living monkeys of East Asia. One of the interesting things from the perspective of paleontology is that this monkey occurs at the same place and same time as ancient apes in Asia.”
Professor Jablonski and colleagues studied the 6.4-million-year-old lower jawbone and the upper portion of the leg bone found in the Shuitangba mine.
The two specimens were found in close proximity and are probably from the same individual of Mesopithecus pentelicus.
Also uncovered slightly lower was a left calcaneus (heel bone) that belongs to the same species.
This specimen was examined by a research team led by Dr. Dionisios Youlatos from the Aristotle University of Thessaloniki and Dr. Xueping Ji from the Yunnan Institute of Cultural Relics and Yunnan University.
“The significance of the calcaneus is that it reveals the monkey was well adapted for moving nimbly and powerfully both on the ground and in the trees,” Professor Jablonski said.
“This locomotor versatility no doubt contributed to the success of the species in dispersing across woodland corridors from Europe to Asia.”
The jawbone and the upper portion of the leg bone indicate that the individual was female.
They suggest that these monkeys were probably ‘jacks of all trades’ able to navigate in the trees and on land.
The teeth indicate they could eat a wide variety of plants, fruits and flowers, while apes eat mostly fruit.
“The thing that is fascinating about this monkey, that we know from molecular anthropology, is that, like other colobines (Old World monkeys), it had the ability to ferment cellulose,” Professor Jablonski said.
“It had a gut similar to that of a cow.”
These monkeys are successful because they can eat low-quality food high in cellulose and obtain sufficient energy by fermenting the food and using the subsequent fatty acids then available from the bacteria. A similar pathway is used by ruminant animals like cows, deer and goats.
“Monkeys and apes would have been eating fundamentally different things,” Professor Jablonski said.
“Apes eat fruits, flowers, things easy to digest, while monkeys eat leaves, seeds and even more mature leaves if they have to.”
“Because of this different digestion, they don’t need to drink free water, getting all their water from vegetation.”
These monkeys do not have to live near bodies of water and can survive periods of dramatic climatic change.
“These monkeys are the same as those found in Greece during the same time period,” Professor Jablonski said.
“Suggesting they spread out from a center somewhere in central Europe and they did it fairly quickly. That is impressive when you think of how long it takes for an animal to disperse tens of thousands of kilometers through forest and woodlands.”
While there is evidence that Mesopithecus pentelicus began in Eastern Europe and moved out from there, the exact patterns are unknown, but the dispersal was rapid in evolutionary terms.
During the end of the Miocene when this monkey species was moving out of Eastern Europe, apes were becoming extinct or nearly so, everywhere except in Africa and parts of Southeast Asia.
“The Late Miocene was a period of dramatic environmental change,” Professor Jablonski said.
“What we have at this site is a fascinating snapshot of the end of the Miocene — complete with one of the last apes and one of the new order of monkeys.”
“This is an interesting case in primate evolution because it testifies to the value of versatility and adaptability in diverse and changing environments.”
“It shows that once a highly adaptable form sets out, it is successful and can become the ancestral stock of many other species.”
The research appears in two papers in the Journal of Human Evolution.
Nina G. Jablonski et al. 2020. Mesopithecus pentelicus from Zhaotong, China, the easternmost representative of a widespread Miocene cercopithecoid species. Journal of Human Evolution 146: 102851; doi: 10.1016/j.jhevol.2020.102851
Xueping Ji et al. 2020. Oldest colobine calcaneus from East Asia (Zhaotong, Yunnan, China). Journal of Human Evolution 147: 102866; doi: 10.1016/j.jhevol.2020.102866