Researchers from Dartmouth University (Dartmouth, England) discovered why the human ancestor had elbows and shoulders. Scientists’ work on display magazine Royal Society Open Science.
The authors used a special program to analyze videos showing how chimpanzees and smoky mangabeys move through trees in the wild. According to the researchers, the chimpanzee’s hand structure is more human-like.
It is the shoulder joint in the form of a shallow socket under the rounded outer part of the humerus. Adapts to dislocations more easily, but provides a greater range of motion. Chimpanzees can also fully extend their arms, thanks to the special structure of their elbows. Mangabei, on the other hand, look more like four-legged animals.
“We found that when climbing trees, chimpanzees and mangabeys have greater joint angles of inclination of the shoulders and elbows, so primates do the same. However, as the chimpanzees descended from the trees, they extended their arms over their heads to hold on to the branches,” the scientists noted.
To them, this suggests that the ancient ancestors of humans and other primates developed human arms to slow the descent from trees. The large size of the body makes the usual descent dangerous due to the high risk of falling – the movable elbows and shoulders act as brakes, not allowing it to fall.
“This is the same anatomy as the first monkeys, but with a few changes. You now have a body part that can throw spears or stones to defend yourself, grab something you need, or help you climb somewhere. The descent from the tree laid the anatomical basis for the event that developed millions of years later. In American football, when a quarterback throws the ball, this movement originates from our ape ancestors,” the scientists concluded.
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