The shoulder shape is holding the key to understanding human evolution and how they shifted to a life out of tree, new research suggest.
Recent research says that humans and chimpanzees have African ape-like common ancestors.
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The conclusion was drawn after examining the shoulder bone and it was found that was a sustained change in the shape of the shoulder which occurred during human evolution from African ape-ancestor to a modern human form.
For the study, researchers at University of California, San Francisco compared 3-D measurements of fossil shoulder blades of early humans and modern humans against African apes, chimps, orangutans, gibbons and monkey.
The findings are crucial in terms of understanding human evolution and how they shifted to a life away from the trees gradually, over time.
“Humans are unique in many ways,” said Nathan Young, lead author of the study. “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.”
The shoulder bone seems to provide a missing link for human evolution. The human lineage separated from chimpanzees about 6 or 7 million years ago. It is also important to find how the anatomy and behavior of both lineages changed over the time but, human fossil record is sparse and little is known about the earliest members of our lineage.
There are many competing theories regarding how the early human ancestor looked like. “Our study suggests that the explanation, that the ancestor looked a lot like a chimp or gorilla, is the right one, at least in the shoulder.” Young said.
The shoulders of modern African apes consist of trowel shaped and a handle like spine that gives an advantage to the arms when climbing the trees or swinging through the branches whereas human shoulder blades are unique and different from all the apes. It shares a lateral orientation with orangutans unlike African apes.
“These data suggest a long, gradual shift out of trees and increased reliance on tools as our ancestors became more terrestrial.” Study wrote.
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The study was published in PNAS.