When you walk out the door to start your day, you may not know you’re participating in something that defines us as humans — and something our ancestors have been doing for seven million years, according to new research.
Scientists analyzed a femur and two arm bones from Sahelanthropus tchadensis, one of the earliest known human ancestors, and found signs that they walked on two feet — also known as bipedalism, according to a new study published in the journal Nature.
“Our oldest known representatives practiced bipedalism (on the ground and in trees),” said study author Franck Guy, a researcher at the Université de Poitiers in France.
Remnants of ancient beings show that bipedalism arose soon after chimpanzees and human ancestors diverged on their evolutionary paths, he added.
There is even more to be found in these fossils. Its features show that Sahelanthropus tchadensis also retained the ability to climb trees proficiently, according to the study.
These ancestors were hominids, or species more closely related to humans than chimpanzees, and mark an early stage in our evolutionary divergence, said Daniel Lieberman, a professor of human evolutionary biology and paleoanthropologist at Harvard University. Lieberman was not involved in the study.
The bipedalism in these ancestors is not exactly a surprise. The arm and leg bones analyzed in this study were found in Chad in 2001 alongside a nearly complete skull, the study said. It’s unclear whether they came from the same individual, said study author Guillaume Daver, assistant professor of paleontology at the Université de Poitiers.
The skull showed a point pointing downwards where the head and spinal cord meet — a feature that would make walking on all fours much more difficult, Lieberman said.
The new analysis by members of that discovery provides even more evidence that hominids were traveling on two legs when they roamed the Earth about 7 million years ago, he added.
“It’s a glimpse into what put the human lineage on an evolutionary path separate from our ape cousins,” Lieberman said. While recent findings support what early studies have already suggested, fossils from this era are rare, so each discovery is important evidence, he added.
And the new study “makes it quite unlikely that the common ancestor we share with chimpanzees looks like a chimpanzee,” Guy said.
bipedalism
Bipedalism was extremely important to our evolution, but it didn’t make much sense to our ancestors, Lieberman said.
Walking on two legs makes the animal slower, more unstable and more at risk for back pain, none of which are useful for survival, he added.
“There must have been some pretty big upside,” Lieberman said. Scientists have a hypothesis about what could have been.
Our common ancestor with apes was a lot like a chimpanzee, and we know they need to use a lot of energy to walk — twice as much as humans when you adjust for body size, Lieberman said.
When the evolutionary paths of humans and chimpanzees diverged, Earth’s climate was changing and tropical forests in Africa were breaking up, so our ancestors had to travel farther to get food, he said. The hypothesis is that walking on two legs gave them more energy to travel.
“What really put us on this different evolutionary path is that we were bipedal, or walked on two legs,” Lieberman said. “It helps us really understand the origins of humanity.”
There are many things that define us as humans, such as language, tools and fire, he said. And in the 1870s, Charles Darwin — without any of the evidence we have now — guessed that walking on two legs was the spark that started it all, Lieberman said.
And now we can see that bipedalism was a big differentiator for apes and helped free up our hands to develop tools, Lieberman said.
“We proved Darwin right,” he said. “This is cool.”
Source: CNN Brasil
