It’s a dispute that has taken a long time to reach boiling point. Seven million years after an ape-like creature – since dubbed Toumaï – traversed the landscape of modern Chad, its mode of transportation has sparked a dispute among fossil experts. Some claim this is the oldest member of the human lineage. Others that it was just an old monkey.
The series, sparked by a paper in Natureled scientists to denounce opponents last week, while others accused rivals of basing theories on “less than five-minute observation”.
The heart of the dispute is simple. Could Toumaï – meaning “hope of life” in Chad’s local Daza language – walk on two legs, an ability that suggests it might actually be the oldest member of the human family? The scientists who excavated the fossil remains believe this is the case.
Others vehemently disagree. They say Toumaï – a member of an extinct species known as Sahelanthropus tchadensis – was not two-legged, but moved on all fours like a chimpanzee. Claims of ancient human ancestry are false, they argue, accusing opponents of cherry picking.
The dispute is bitter even for paleontology, a field known for the bitterness of its controversies over the interpretation of ancient skulls and bones. In this case, the controversy began with the discovery in 2001 of a distorted skull and other bones by paleontologists from France and Chad in the Djurab desert. They concluded that the skull’s shape meant it must have belonged to a creature that walked upright.
“It’s very emotional to have the beginning of the human lineage in my hands,” said a member of the team at the time, Michel Brunet of the University of Poitiers. The find made Brunet a scientific star in France, particularly in Poitiers, where a street is named after him.
However, the interpretation was based solely on examination of the skull, critics said. The other bones were put aside until examined in 2004 by Aude Bergeret-Medina, also of the University of Poitiers. She recognized a leg bone and concluded that it was from a primate that walked on all fours—not two. Crucially, she was supported by her superior, Roberto Macchiarelli.
It took Macchiarelli and Bergeret more than a decade to publish their conclusions. Attempts to present their findings to the Anthropological Society of Paris were blocked, while Macchiarelli was accused of scientific misconduct by his opponents.
An account of their work eventually concluded that Toumaï was a four-legged creature and probably not a founder of the human lineage. “The evidence for bipedalism is very, very tenuous,” says Macchiarelli.
Last month, the finders of the skull and bones published their answer in Nature and said examination of the bones indicated bipedalism, suggesting that it had a closer relationship with humanity than did apes. One of the team, Franck Guy, took to Twitter to accuse Macchiarelli and his colleagues of basing their conclusions on a 5-minute observation and a few photos. “Our paper is a five-year study,” he added.
Other scientists, including Professor Bernard Wood of George Washington University, have been vocal in dismissing Guy’s claims while supporting the argument that Toumaï’s bones suggest he was chimpanzee-like.
Professor Chris Stringer of the Natural History Museum in London was more cautious. “It’s a shame that these disputes distract from the really important finds,” he told the observer. “Given the peculiar and largely unknown circumstances of the find – the bones looked like someone had collected them and placed them in the desert sand – we don’t even know if the skull, leg, and arm bones belong together as a single individual.
“I would say the jury is still out on whether Toumaï was fully adapted to walking on two legs.”