It is a dispute that has taken a long time to reach boiling point. Seven million years after an apelike creature – since nicknamed Toumaï – traversed the landscape of modern Chad, its means of mobility has triggered a dispute among fossil experts. Some claim this was the oldest member of the human lineage. Others that it was just an old ape.
The row, kindled by a paper in Nature, last week led scientists to denounce opponents while others accused rivals of building theories on “less than five minutes’ observation” .
The core of the dispute is straightforward. Could Toumaï – which means “hope of life” in the local Daza language of Chad – walk on two feet, an ability that suggests it could indeed be the oldest member of the human family? The scientists who unearthed the fossil remains believe this is the case.
Others disagree, vehemently. They say Toumaï – a member of an extinct species known as Sahelanthropus tchadensis – was not bipedal but moved around on all fours like a chimpanzee. Claims of ancient human ancestry are false, they argue, accusing opponents of cherry-picking data.
The dispute is rancorous even for palaeontology, a field noted for the bitterness of its controversies over the interpretation of ancient skulls and bones. In this case, the dispute began with the 2001 discovery in the Djurab desert of a distorted skull and other bones by palaeontologists from France and Chad. They concluded the skull’s shape meant it must have belonged to a creature that walked upright.
“It’s a lot of emotion to have in my hand the beginning of the human lineage,” said one member of the team, Michel Brunet of the University of Poitiers, at the time. The finding made Brunet a scientific star in France, especially in Poitiers, where a street is named after him.
However, the interpretation was based solely on examining the skull, critics said. The other bones had been put aside until they were examined in 2004 by Aude Bergeret-Medina, also of Poitiers University. She recognised a leg bone and concluded it came from a primate that walked on all fours – not two. Crucially, she was backed by her supervisor, Roberto Macchiarelli.
It took Macchiarelli and Bergeret more than a decade to get their conclusions published. Attempts to present their findings at the Anthropological Society of Paris were blocked, they say, while Macchiarelli was accused of scientific misconduct by his opponents.
A report of their work eventually concluded that it did indicate Toumaï was a four-legged creature and unlikely to be a founder of the human lineage. “The evidence to support bipedalism is very, very poor,” says Macchiarelli.
Last month the finders of the skull and bones published their response in Nature and said examination of the bones pointed to bipedalism, suggesting it had a closer relationship to humankind than apes. On Twitter one of the team, Franck Guy, accused Macchiarelli and his colleagues of basing their conclusions on 5 minutes’ observation and a few photos. “Our paper is a five-year study,” he added.
Other scientists, including Prof Bernard Wood, of George Washington University, have been vocal in dismissing Guy’s claims while backing the argument that Toumaï’s bones indicate it was chimpanzee-like.
Professor Chris Stringer of the Natural History Museum, London, was more cautious. “It’s a shame that these disputes detract from what are really important finds,” he told the Observer. “Given the peculiar and largely unacknowledged circumstances of discovery - the bones looked like they had been collected by somebody and placed on the desert sand – we don’t even know if the cranium, 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.”