A new study has indicated that our shoulders hold the key to understanding human evolution. Researchers believe that the last common ancestor that linked humans to chimpanzees might have had shoulders that were very similar to those of present day African apes.

Human began to diverge from chimpanzee somewhere around six (6) or seven (7) million years ago, and many researchers believe that we moved away from tree habitats gradually. The new study backs up this theory.

The more information researchers gather on last common ancestor, the more questions they’ll be able to answer, including that of how exactly the behaviors and the anatomy of both species have evolved throughout the centuries.

Nathan Young, evolutionary biologist with the University of California (San Francisco), gave a statement saying that one of the main things that make it difficult for researchers to explore these questions is that “fossils from that time are rare”.

Right now the scientific community is considering two (2) very different theories related to the look of the last common ancestor. According to the first one, the animal resembled present day African apes (gorillas, chimpanzees) a great deal. And the theory is so accepted that Young explained that “A lot of people use chimpanzees as a model for the last common ancestor”.

But according to the second theory, the similarities found in present day African apes and the last common ancestor might have evolved independently, and that those of the last common ancestor might’ve been more primitive.

For example, the last common ancestor might not have been able to use its knuckles to walk on the ground the same way that gorillas and chimpanzees do. Instead, the animal might have hung from trees and swung from one branch to the other the same way that orangutans do. But orangutans are Asian apes, which would indicate that the last common ancestor shared some traits with this group as well.

Young stressed that we’re not the only species to evolve throughout the centuries – “Chimpanzees and gorillas have evolved and changed over time, too, so looking at their modern forms for insights into what the last common ancestor was like could be misleading in a lot of ways”.

Once field experts are able to have a clear trajectory of how our shoulder evolved, they’ll be able to exampling a lot of behavioral changes – “when exactly did early humans start to rely heavily on their tools?”, “when did they start to spend less time in tress?” and “when and how did they learn to throw weapons?”.

The difficulty in reconstructing this trajectory lies in the fact that human shoulders share traits not only with chimpanzee shoulders, but also with orangutan shoulders.

For their study, Young and his team generated the 3D shoulder models of several museum specimens – gorillas, orangutans, chimpanzees, bonobos, gibbons, monkeys and modern humans. They then compared these models to previously generated 3D shoulder models of ancient, extinct relatives of modern humans.

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