Early "Human" Is Ape After All, Discoverer Decides
for National Geographic News
|June 17, 2009|
Nearly 15 years ago Russell Ciochon shook our family tree when he announced that a fossil found in a Chinese cave was evidence of a new form of early human.
But that was then.
Today the anthropologist announced that the fossil, a partial jaw, is from an ape after all—a "mystery ape." And as controversial as the original theory was, Ciochon's reversal is also meeting with some criticism.
The fossil was found in the 1980s in south-central China's Longgupo cave. According to Ciochon, "the jaw was very perplexing. It didn't fit in any category of hominin [early human ancestor] that we knew of in Asia, and it also didn't fit into any ape category."
Ciochon and colleagues theorized that the fossil represented an unknown hominid who lived in Asia 1.9 million years ago—about a million years earlier than early humans are generally thought to have arrived in the region.
The ancient hominin, Ciochon's team suggested in 1995, was a more primitive species than Homo erectus, the human ancestor thought to have migrated from Africa and populated Asia (interactive map of prehistoric human migrations).
The 1995 theory implied that a line of H. erectus could have evolved independently in Asia.
Teeth Take Bite Out of Theory
As the years passed, Ciochon recounted, new evidence caused him to reconsider the disputed fossil.
First, in 2000 and 2001, scientists showed that the Longgupo jaw had teeth that had strong similarities to those of the older, extinct ape Lufengpithecus, a possible orangutan ancestor.
Then, in 2005, Ciochon examined the large collection of primate teeth from the Pleistocene epoch (about 1.8 million to 11,500 years ago) at the Guangxi Natural History Museum in Nanning, China.
The collection, from a well-documented cave site, included some unidentified primate teeth that strongly resembled those in the Longgupo jaw—and that's when Ciochon was convinced.
"All of a sudden there is more evidence, and when you have more evidence ideas can change," said Ciochon, who details his change of heart in an essay in tomorrow's issue of the journal Nature.
Archaeologist Richard Potts noted that if anyone's qualified to change the conclusions in this case, it's Russell Ciochon.
"Russell has probably seen more isolated teeth of primates from this time period than anyone else," said Potts, director of the Human Origins Program at the Smithsonian Institution in Washington, D.C.
Still, it's unclear to Ciochon, or anyone else, what such mystery apes were like.
Chinese anthropologist Wang Wei from the Guangxi museum is to lead an effort to evaluate, and reevaluate, unidentified primate fossils from around southeastern Asia. The results, it's hoped, will help fill in the ape family tree for the region.
Ciochon's new theory is based on more than a new anatomical analysis.
The mystery-ape fossils were found in what was once a massive subtropical forest. The tooth-yielding caves, for example, house fossils of forest animals such as the elephant-like Stegodon, a prehistoric panda, and the extinct giant ape Gigantopithecus as well as ancestors of orangutans and gibbons.
Early humans, Ciochon hypothesizes, probably could not, or would not, have lived in such a place.
"Through a long history of analyzing fossil sites in Africa where the genus Homo is found, we know that these early humans were living in grassland or savanna-fringe environments," he said.
"If early humans lived in these more open environments in Africa, why would they inhabit a subtropical forest in Asia?"
But the Smithsonian's Potts noted that the prehistoric environment was dynamic and highly variable, and he cautioned against black-and-white designations like "forest" or "grassland."
A typical Pleistocene landscape in the region would likely have been more mixed, including open areas around a swamp or lake, bushy vegetation, and a surrounding highland forest, said Potts, citing recent discoveries of fossil pollen, spores, and sediment at Pleistocene sites.
"I think," Potts said, "that we shouldn't let the environment dictate the taxonomy."
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