A new study from the University of California says that the modern human’s ancestor closely resembled the looks and behaviors of current-day chimps.
The study was based on the discovery of bones that researchers found to be the last common ancestor. But it is still unclear as to what that ancestor looked like, according to Tech Times.
“Humans are unique in many ways,” says lead study author Nathan Young. “We have features that clearly link us with African apes, but we also have features that appear more primitive, leading to uncertainty about what our common ancestor looked like.”
By directly looking at the shoulders, an easy explanation they found would be that the ancestor resembled a chimp or gorilla. The changes in shoulder shape in early humans are clear evidence of new behaviors which include a reduction in tree climbing and then, the first innovation of tool use.
The modern African ape has shoulders that consist of a trowel-shaped blade and a handle-like spine that eases movement of the arm up toward the skull. This is an advantage when climbing trees or swinging through branches.
But in contrast, the should joint is pointed down in modern monkeys humans as well which leads them to evidence of behaviors including stone tool-making the throwing objects like spears or rocks.
Around six or seven million years ago, the human lineage diverged from that of the chimp, which is our closest living relative. The fossils of the earliest possible common ancestor are extremely rare, which has forced researchers to create a 3D model of shoulders taken from museum examples of early hominids, modern humans, chimps, gorillas, monkeys, orangutans and gibbons.
“The mix of ape and human features observed in A. afarensis’ shoulder support the notion that, while bipedal, the species engaged in tree climbing and wielded stone tools,” says Zeray Alemseged, senior anthropology curator at the California Academy of Sciences. “This is a primate clearly on its way to becoming human.”
The study overall suggests a very long and gradual shift down from trees with an increasing reliance on tools that drove the evolution of human lineage.