Were our earliest ancestors from Asia?

Posted by Emma Woollacott

Pittsburgh, PA - A new fossil primate from Myanmar - previously known as Burma - has led researchers to conclude that the common ancestor of humans, monkeys and apes evolved from primates in Asia, not Africa.

A major focus of recent paleoanthropological research has been to establish the origin of anthropoid primates - monkeys, apes and humans - from earlier and more primitive primates known as prosimians. These include lemurs, tarsiers and their extinct relatives. The traditional view has been that anthropoids originated in Africa, but this has been challenged by recent discoveries in China, Thailand, and Myanmar.

Earlier this year, the discovery of the fossil primate skeleton known as Ida in the Messel oil shale pit in Germany led some scientists to suggest that anthropoid primates evolved from lemur-like ancestors known as adapiforms.
 
But according to Dr Chris Beard – a paleontologist at Carnegie Museum of Natural History in Pittsburgh, Pennsylvania - the new primate, Ganlea megacanina, shows that early anthropoids originated in Asia rather than Africa. These early Asian anthropoids differed radically from adapiforms like Ida, indicating that Ida is more closely related to modern lemurs than to monkeys, apes and humans.

The 38-million-year-old Ganlea megacanina fossils, excavated at multiple sites in central Myanmar, belong to a new genus and species. Greatly enlarged canine teeth distinguish the animal from closely related primates, and heavy dental abrasion indicates that Ganlea megacanina used its teeth to pry open the hard exteriors of tough tropical fruits in order to extract the seeds.

"This unusual type of feeding adaptation has never been documented among prosimian primates, but is characteristic of modern South American saki monkeys that inhabit the Amazon Basin," says Dr Beard. "Ganlea shows that early Asian anthropoids had already assumed the modern ecological role of modern monkeys 38 million years ago."

Ganlea belongs to an extinct family of Asian anthropoid primates known as the Amphipithecidae. Two other amphipithecids were previously discovered in Myanmar, while a third was found in Thailand. A detailed analysis of their evolutionary relationships shows that amphipithecids are closely related to living anthropoids and that all of the Burmese amphipithecids evolved from a single common ancestor. Some scientists had previously argued that amphipithecids were not anthropoids at all, being more closely related to the lemur-like adapiforms.
 
The discovery of Ganlea strongly supports the idea that amphipithecids are anthropoids, because adapiforms never evolved the features that are necessary to become specialized seed predators. Indeed, all of the Burmese amphipithecids appear to have been specialized seed predators, filling the same ecological niche occupied by modern pitheciine monkeys in the Amazon Basin of South America. During the Eocene when Ganlea and other amphipithecids were living in Myanmar, they inhabited a tropical floodplain very similar to the modern Amazon Basin.

The  research is published online in the Proceedings of the Royal Society B (Biological Sciences).