A couple of decades ago, anthropologists unearthed an enigmatic ape-like fossil that roamed the Sahara region over 7 million years ago. It didn’t fit neatly into their existing understanding, but it was clearly significant. Now, a new study has weighed in on the bones with more evidence that this species walked on two legs and may be the oldest-known member of the “human” family.
The species in question is Sahelanthropus tchadensis, whose remains were discovered in the early 2000s in the Djurab Desert of northern Chad.
From the moment it was unearthed, the fossil sparked intense debate about its identity and place on the evolutionary family tree. Was it an ancient ancestor of gorillas or chimpanzees? Or, more provocatively, could it be directly related to hominins, the branch on the family tree where we hang along with extinct human species and all our immediate ancestors, like Neanderthals, Homo erectus, and the like?
In the new paper, researchers reanalyzed the specimen’s bones using advanced 3D imaging and other modern techniques. They then compared its shape and structure to the same bones of living and fossil species, including the famous “Lucy” specimen.
Another comparison of chimpanzee, Sahelanthropus, and Homo sapiens (left to right).
Image Credit: Scott Williams/NYU and Jason Heaton/University of Alabama Birmingham
Their work identified a distinct femoral tubercle, a feature on the thigh bone that serves as the attachment point for the iliofemoral ligament. This is the largest and most powerful ligament in the human body, used to keep the hips stable and assist the movement of walking.
According to the researchers, this strongly suggests that Sahelanthropus was capable of bipedal locomotion.
“Sahelanthropus tchadensis was essentially a bipedal ape that possessed a chimpanzee-sized brain and likely spent a significant portion of its time in trees, foraging and seeking safety,” Scott Williams, an associate professor in New York University’s Department of Anthropology who led the research, said in a statement.
“Despite its superficial appearance, Sahelanthropus was adapted to using bipedal posture and movement on the ground.”
Some previous work has also argued that Sahelanthropus walked upright, while other research has suggested it primarily moved on all fours like a knuckle-dragging ape. This latest research adds weight to the idea that the species may have been more human-like and bipedal than previously thought.
Although the size of the Sahelanthropus legs was relatively short, more similar to chimps, the proportions were more hominin-like. Crucially, there was also evidence that it had strong gluteal muscles ( that’s basically the butt muscle) similar to those in other early hominins.
Altogether, this indicates that the species may represent some of the earliest adaptations to bipedalism in the hominin lineage, making it a pivotal character in the story of humans.
“Our analysis of these fossils offers direct evidence that Sahelanthropus tchadensis could walk on two legs, demonstrating that bipedalism evolved early in our lineage and from an ancestor that looked most similar to today’s chimpanzees and bonobos,” concludes Williams.
The new study is published in the journal Science Advances.
Source Link: Mysterious 7-Million-Year-Old Ape May Be Earliest Hominin To Walk On Two Feet
