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Ape Fossil Found in Thailand—May Be Orang Ancestor

Stefan Lovgren
for National Geographic News
March 6, 2003
 
Researchers have unearthed a fossil ape that dates back 10 to 13.5 million years and could be an ancestor to the orangutan. The species, Lufengpithecus chiangmuanensis, was found in Thailand. It's the first fossil ape that has been discovered in the region where orangutans live today.

The fossils were found during a six-year survey of a coal mine in northern Thailand. They consist of 22 isolated teeth from both the upper and lower jaws of several apes.

"It's the first time an ancestor of an extant ape has been identified in the old fossil record [more than 10 million years]," said Jean-Jacques Jaeger, professor of paleontology at France's University of Montpellier, whose research team made the discovery.


Apes have a poor fossil record. Anthropologists hope the new find will lead to additional discoveries, which could help piece together the evolutionary puzzle of apes and even shed new light on human evolution.

Murky History

Modern orangutans hail from the Pleistocene era, 2 million to 100,000 years ago. Their geographic distribution once included much of Southeast Asia. However, they became extinct from many areas because of deforestation and hunting. Today, the orangutan can only be found in Borneo and Sumatra.

The orangutan is the only great ape with a fossil record. (Strangely, no African fossil has ever been found that is related to chimpanzees or gorillas.) But determining the ancestry of the orangutan has proven extremely difficult.

Previous discoveries of the orangutan's extinct relatives have been dismissed as possible ancestors. Sivapithecus, which lived in Pakistan 8 to 12.8 million years ago, had a face like an orangutan but its teeth and lower jaw are different. Its skeleton shows it to have walked on all fours, like a baboon. Lufengpithecus, which lived in southern China 8 to 9 million years ago, had a dental structure with no analog among apes living today.

"The new Thai fossil ape shares many dental characters with that Lufengpithecus, but it has a less specialized anterior dentition, similar to that of orangutan," said Jaeger. "It appears to be the best candidate to represent the ancestor or a species closely related to the ancestor of orangutan."

Some experts warn against establishing ancestry by comparing teeth because animals can have similar dental structures and still be very different. The new fossil could be a close relative of the orangutan, but perhaps not an ancestor.

Researchers don't know how the different relatives were related to each other. "Maybe they evolved in another place, like Arabia for instance, which is not well documented," said Jaeger.

Links to Africa

The fossils were found in a lignite (a type of coal) mine, located in what used to be a swampy and shallow lake deposit. The rocks containing the teeth also hold fossil plants of the Syzygium tree, which produce edible fruits called "champoo" that are still available in southeast Asian fruit markets.

Jaeger believes the fossil ape came to collect these fruits at the lake. Some apes were killed by predators such as crocodiles when they went to drink out of the lake. Others may have been killed by tigers and panthers in the forest.

Syzygium is affiliated with existing East African plant communities, suggesting that a tropical forest belt extended from East Africa to South Asia around 10 to 14 million years ago. "This belt would have allowed free circulation in both directions, at least for tropical forest dwellers," said Jaeger.

Even if the fossil ape is the ancestor to the orangutan, it didn't look like the modern ape. "Evolution basically redesigned apes," said David Pilbeam, professor of anthropology at Harvard University. "Just about every feature of living apes—their torsos, internal organs, ligaments, and joints—is different from their more primitive kin."

The fossil ape probably weighed about 70 pounds (26 kilograms). No known fossil ape is adapted for life in the trees, and Jaeger believes orangutans may therefore be descended from a ground-dweller.

Man and Ape

The discovery could shed new light on the common ancestry of apes and humans. "Very little is known about human evolution in the period 14 to 4 million years ago, during which time the human line split from its more ape-like ancestors and relatives," said Pilbeam.

An international team of medical researchers and anthropologists recently determined that a gene mutation found only in humans and not in our evolutionary cousins, the apes, occurred more than two million years ago, just prior to human brain expansion but after human ancestors stood upright.

"The evolution of early hominines [the ancestors of modern humans] cannot be fully understood as long as the history of extant apes is not clearly situated in time and space," said Jaeger.

A summary of Jaeger's research appears in the current issue of the science journal Nature.
 

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