Ancient Ancestor Combines Human and Ape Traits: Fossils Reveal Evolution of Humans

There may be new insights into the early ancestors of humans. Researchers have described the anatomy of an ancient hominim in six new studies. The findings reveal how our two million year old ancestor walked, talked, chewed and moved.

The fossils of our early ancestor, named Australopithecus sediba, were first discovered four years ago in Malapa near Johannesburg. The site has yielded more than 220 bones of early hominins, representing more than five individuals. They include the remains of babies, juveniles and adults. Interestingly, they show a mixture of features--a primitive ribcage combines with a more modern thorax and slim waist. The combination of these features has made researchers believe that these fossils could be evidence of an extremely early ancestral form of the genus Homo.

This particular study focused on how this early species moved rather than how it compared to human evolution. The narrow upper thorax of apes enables them to move the shoulder blade, which is crucial for climbing in trees. The same trait is possessed by the fossil, which makes the researchers believe that the species could not walk or run on both feet as well as humans.

"They probably couldn't run over long distances, especially as they were unable to swing their arms, which saves energy," said Peter Schmid, one of the researchers, in a press release.

While it's likely that they couldn't run on both feet as well as humans, the researchers did find that Au. sediba had the same number of lumbar vertebrae as modern man. More specifically, it possessed a strong, hollow back. This made it more advanced in that area than other species.

"From a distance, I'm not sure one would notice differences between sediba and human walking," said Jeremy DeSilva, one of the researchers who analyzed the species' lower skeleton, in an interview with NewScientist. "But if you could get closer, you might notice something. It wouldn't heel-strike like a modern human does. It would take short, quick steps. And there would also be a tremendous amount of rotation and inward twisting of the foot, knee and hip."

The teeth also showed similarities to humans. In fact, parts of the lower jaw appear to most resemble representatives of early Homo.

"Such clear insight into the anatomy of an early hominin species will clearly have implications for interpreting the evolutionary processes that affected the mode and tempo of hominin evolution and the interpretation of the anatomy of less well preserved species," said Lee Berger, the project leader, in an interview with Phys.org.

The set of studies were published in the journal Science.

Want to see images of the skeleton? Check them out here.