July 2, 2009

Fossils Might Change Human Origin Theories

Researches reported on Wednesday that fossils recently discovered in Myanmar might prove that the common ancestor of humans, monkeys and apes evolved from primates in Asia and not Africa.

However, other scientists say that the finding does not end the debate over the origin of anthropoids, which is the primate group that includes ancient species as well as modern humans.

Dr. Chris Beard, who is a paleontologist at the Carnegie Museum of Natural History in Pittsburgh and a member of the team that found the fossils, said that the pieces of the 38 million-year-old jawbones and teeth found close to Bagan, Myanmar in 2005 show typical primate characteristics.

"When we found it, we knew we had a new type of primate and basically what kind of primate it was," Beard said in a telephone interview from Pittsburgh. "It turns out that jaws and teeth are very diagnostic. ... They are almost like fingerprints for fossils like this."

The report was published in the Proceedings of The Royal Society B, which is a journal based in London.

Beard and his team, which were from France, Thailand and Myanmar, concluded that the fossils came from 10 to 15 individuals of a new species that belonged to an extinct family of Asian anthropoid primates known as Amphipithecidae.

Beard said that they found wear and tear on the canine teeth, which suggests the monkey-like long tailed creatures used their teeth to crack open tropical fruit to get to the pulp and seeds.  This same behavior familiar with that of modern South American saki monkeys that inhabit the Amazon basin.

"Not only does Ganlea look like an anthropoid, but it was acting like an anthropoid 38 million years ago by having this feeding ecology that was quite specialized," Beard said.

The researchers found that the fossil was 38 million years old, which makes it the oldest anthropoid fossil ever found in Africa and the second oldest discovered in all of Asia.

Beard and his Chinese colleagues found fossilized foot bones, in 1994, of the anthropoid Eosimias.  The Eosimias was one of the world's smallest primates and lived between 40 million and 45 million years ago and they roamed in ancient rain forest along the eastern coast of China.

Beard said that both of the fossils' ages help him contend the theory that anthropoid primates evolved in Africa, where Lucy was discovered in 1974.

"This new fossil Ganlea definitely helps us argue "” and we think the argument is pretty close to settled now "” that when you go back this far in time, the common ancestor of monkeys, apes and humans was definitely in Asia, not in Africa," Beard said.

Researchers unveiled a skeleton in May that was nearly intact and was a 47 million-year-old primate.  The find, which was discovered in Germany, was dubbed as "Ida" and the researchers said that it provides a glimpse into how our distant ancestors might have looked.

"We wouldn't claim Ganlea is missing link, but we know Ganlea is much more closely related to our ancestors than Ida ever was "” even though, unfortunately, we don't have complete skeleton like they did for Ida," he said.

The man who brought Ida to the University of Oslo Natural History Museum, Jon Hurum, said that it was to soon for any conclusions to be drawn from the Myanmar fossils because only jawbones and teeth were found.

"These fragments are still too few and far between," Hurum said. "This is the kind of scientific debate that will continue until more complete skeletons like Ida has been found, and this may take several hundred years."

Paleontologist John G. Fleagle, a professor at the Stony Brook University, said the discovery of Ganlea is important because it shows how different primates found in Myanmar are related, as well as providing interesting suggestions regarding a unique dietary specialization.

However, he said that the fossils found in Myanmar do little to prove the origin of anthropoids.

"This doesn't add anything new about whether anthropoids came from Africa or Asia or the broader evolutionary relationships of these particular primates," Fleagle said.

"The definitive features that would resolve it in people's mind would be in the skull," he said. "Without a skull to demonstrate the distinctive anthropoid features of the eye and ear regions, scientists will still continue to debate whether the dental similarities just indicate similar diets or are the result of a common heritage."

Beard said that he is not letting the criticism stop him because he and his team are returning in November to Myanmar to continue a search for more fossils and explore how anthropoids evolved in Asia and later migrated to Africa.

"The question is when and how did this big evolutionary shift occur from Asia to Africa," Beard said. "That is something we are trying to establish. We have a team working in Myanmar which has ideas of places to go in Africa to try and pick up thread there."


Image Caption: A new fossil primate from Myanmar (previously known as Burma) suggests that the common ancestor of humans, monkeys and apes evolved from primates in Asia, not Africa as many researchers believe. The greatly enlarged canine teeth distinguish the animal from closely related primates. Heavy dental abrasion indicates that Ganlea megacanina used its enlarged canine teeth to pry open the hard exteriors of tough tropical fruits in order to extract the nutritious seeds contained inside. Credit: Dr. Laurent Marivaux


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