Humans can rotate their shoulders and extend their elbows, which allows them to do many things, such as reaching, throwing, or working.
But how did these movements evolve? A new study suggested that they came from a natural braking system for our primate ancestors who needed to climb down from trees safely.
The importance of downclimbing in ape evolution
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The study, done by researchers from Dartmouth College, used software to compare the climbing movements of chimpanzees and mangabeys, a type of small monkey, in the wild.
They found that both species climbed up trees in a similar way, with their shoulders and elbows mostly bent close to their bodies.
However, when climbing down, chimpanzees stretched their arms above their heads to hold branches, like a person going down a ladder, while mangabeys kept their arms close to their sides.
The researchers explained that this difference was because of the greater weight of chimpanzees, which made them use their arms as a braking mechanism to slow down their descent and avoid falls.
They also noted that the shoulders and elbows of chimpanzees are very similar to those of modern humans, suggesting that they have a common ancestor who also used this technique.
The lead author of the study and a graduate student at Dartmouth, Luke Fannin, said that their study showed the idea of downclimbing as a very important factor in the different anatomical differences between monkeys and apes that would later show up in humans.
The implications for human evolution and adaptation
The researchers argued that the ability to rotate the shoulders and extend the elbows was not only useful for climbing down from trees but also for adapting to new environments and challenges.
For example, when early humans left the forests for the grasslands, they could use their flexible limbs to gather food, use tools, hunt, or protect themselves.
Fannin said that even after humans started walking upright, the ability to climb and descend trees was still important for survival.
He said that the basic structure of our modern skeletons still shows our ape ancestry.
The study also gave some insight into how climate change may affect the future of primates and humans.
The researchers warned that cutting down trees and losing habitat may reduce the chances for primates to practice their downclimbing skills, which could have bad consequences for their survival and evolution.
A co-author of the study and a professor of anthropology at Dartmouth, Jeremy DeSilva, said that movement in humans is a great example of evolutionary compromises.
He said that we need to understand how our ancestors moved to understand how we move today and how we might move in the future.
Some of the other adaptations that early humans had are:
Tool-making:
Early humans learned how to make and use tools from stone, bone, wood, and other materials. Tools helped them to hunt, cut, scrape, dig, and perform other tasks more efficiently and effectively.
Tool-making was a major adaptation for early humans, as it gave them an advantage over other animals and increased their chances of survival and reproduction.
Fire:
Early humans discovered how to control fire and use it for various purposes. Fire provided them with warmth, light, protection, and cooking.
Fire also allowed them to expand their range into colder and darker regions. It was a crucial adaptation for early humans, as it improved their quality of life and enabled them to cope with environmental changes.
Language:
Early humans developed the ability to communicate with each other using sounds, gestures, and symbols.
Language facilitates social interaction, cooperation, learning, and cultural transmission. It was a fundamental adaptation for early humans, as it enhanced their cognitive and social skills and allowed them to express their thoughts and emotions.
