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New Fossil Primate Challenges "Missing Link" Ida

1 July 2009 (All day)
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(fossil) Laurent Marivaux; (primates) Mark A. Klingler/Carnegie Museum of Natural History

Meet Ganlea. A new fossil of a primate from Myanmar suggests that the ancestor of apes, monkeys, and humans was from Asia.

Remember Ida? It's been just a month since the fossil primate made her debut on the History Channel where she was called a "missing link" between humans and primitive primates and a "revolutionary scientific find that will change everything." But Ida may be robbed of her claim to that title by a new fossil primate from Asia, published today. "It shows that Ida is out of the running as a [human] ancestor," says the fossil's discoverer, paleontologist K. Christopher Beard of the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania.

Researchers have long searched for the earliest anthropoids, advanced primates that were the ancestors of humans, apes, and monkeys. Until recently, most scientists thought anthropoids arose in Africa, where the oldest widely accepted members of the group lived as early as 37 million years ago in the Fayum province of Egypt.

But recent evidence has pointed to an Asian origin. Fossils from that continent suggest that the first anthropoids could have been either Eosimias, a genus of tiny primates that lived 4 million to 45 million years ago, or a younger group called amphipithecids. Then came Ida. Her discovery in an oil shale pit in Germany suggested to a handful of paleontologists that a third group of primates, called adapids, might have given rise to the first primitive anthropoids instead, this time from Europe--although few experts in primate origins agreed.

Now, the newest find tips the scales back in favor of the Asian origin of anthropoids. In 2005, Beard discovered a 37-million-year-old jaw fragment in the badlands of central Myanmar. The jaw belonged to an amphipithecid, which Beard and paleontologist Jean-Jacques Jaeger of the University of Poitiers in France have named Ganlea megacanina in the Proceedings of the Royal Society B. Although the fossil is not nearly as dazzling as a complete skeleton of Ida, Beard knew immediately that the jaw was something special. It has a huge canine tooth, which was used to pry open the hard shell of tough tropical fruits to eat the seeds, according to wear markings. That's an unusual feeding adaptation found in modern saki monkeys in the Amazon Basin of South America.

This monkeylike behavior, as well as anatomical features in other fossils of amphipithecids from Asia, adds new evidence to the view that amphipithecids were early anthropoids and, hence, that anthropoids arose in Asia, says Beard. Others agree: These fossils "affirm the importance of Asia as a hotbed of early anthropoid evolution," says paleontologist Callum Ross of the University of Chicago in Illinois.

Not so fast, says paleoanthropologist Russell Ciochon of the University of Iowa in Iowa City. Although he agrees that anthropoids arose in Asia, he would like to see more evidence than just a fragmentary jaw. The new fossil, he says, does "nothing to provide resolution to the anthropoid origins debate." Ross counters that the new fossil is indeed important. It "provides important independent confirmation that Asian amphipithecids are closely related to [the most primitive] anthropoids," he says.

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