“Our oldest known representatives are bipedal (on the ground and in trees),” said study author Frank J., a researcher at the University of Poitiers in France. He said ancient remains show that bipedalism arose soon after chimpanzee and human ancestors separated on their evolutionary path.
Much more can be found in these fossils. According to the study, their characteristics suggest that Sahelanthropus tachadensis also has the ability to climb trees efficiently.
These ancestors were species more closely related to humans than hominins or chimpanzees, and they represent an early stage in our evolutionary divergence, said Daniel Lieberman, professor of human evolutionary biology and paleontologist at Harvard University. Lieberman was not involved in this study.
It is no surprise in this ancestor to walk on two legs. The arm and leg bones analyzed in the study were found in Chad in 2001, along with almost complete skulls, the study said. Study author Guillaume Davar, assistant professor of paleontology at the University of Poitiers, said it was unclear whether they belonged to the same individual.
Lieberman said the skull shows a downward-pointing point where the head and spine meet—a feature that would have made it difficult to move around.
A new analysis of the limbs from this discovery provides more evidence that hominins traveled on two legs when they roamed the Earth about 7 million years ago, he said.
“It’s a glimpse into what has put the human lineage on an evolutionary path apart from our ape cousins,” Lieberman said. Supporting recent findings, he said, support recent findings that early studies suggested, fossils from this time period are rare, so any finds are significant evidence.
The new study “reduces the possibility that our common ancestor with chimpanzees is very similar to chimpanzees,” Guy said.
Walking on two legs starts a fire
Lieberman said that walking on two legs was very important for our evolution, but it meant nothing to our ancestors.
They said that walking on two legs made the animal slower, more erratic and at greater risk for back pain, neither of which was beneficial for survival.
“There should be a huge advantage,” Lieberman said. Scientists have hypotheses about what could have happened.
Our common ancestor with apes was very similar to chimpanzees, Lieberman says, and we know they needed to use a lot of energy to walk — twice as much as humans when adapted to body size.
When humans and chimpanzees parted ways, they say, Earth’s climate changed and Africa’s rainforests fragmented, so our ancestors had to move further away in search of food. The hypothesis is that walking on two legs gives them more energy to travel.
“What really pushed us down this different evolutionary path was that we walked on two legs, or did we walk on two legs,” Lieberman said. “It helps us really understand human origins.”
He says that there are many things that define us as human beings, such as language, tools and fire. Lieberman says that in the 1870s Charles Darwin conjectured – without the evidence we have today – that walking on two legs was the spark that started it.
We can now see that walking on two legs is a huge difference from monkeys and that the tool helps free up our hands for evolution, says Lieberman.
“We have proved Darwin right,” he said. “It’s great.”