New research conducted by Dartmouth scientists has revealed that apes and early humans developed flexible shoulders and elbows in order to navigate trees safely. These adaptable appendages played a crucial role in the ability of early humans to gather food and use tools for hunting and defense.
The researchers utilized sports-analysis and statistical software to compare videos and still-frames of chimpanzees and mangabeys climbing in their natural habitats. They discovered that chimpanzees extended their arms above their heads, much like a person descending a ladder, to slow their descent as gravity pulled on their heavier bodies. This technique, known as “downclimbing,” had previously been underestimated in terms of its impact on the evolution of apes and early humans.
Early apes evolved in dispersed forests where they would climb up a tree to obtain food and then descend to move on to the next tree. As a result, natural selection favored anatomical features that allowed these creatures to safely come down from trees. The flexible shoulders and elbows of early humans enabled them to climb trees during the night for safety and descend unharmed in daylight.
Interestingly, the human form developed broader shoulders capable of a 90-degree angle, along with free-moving shoulders and elbows. These features made our ancestors adept at using tools such as spears. The study also revealed that chimpanzees’ arms bear a striking resemblance to those of modern humans, suggesting that descending from trees was likely a challenge for our early ancestors as well.
In contrast to monkeys, which have deeper shoulder sockets and elbows with protruding olecranon processes, chimps and humans possess shallow ball-and-socket shoulders and reduced-length elbow bones that allow for fully extended arms. This increased flexibility in the shoulder and elbow joints may explain why apes evolved greater range of motion in these areas.
Descending from trees for chimpanzees is a controlled fall that requires deceleration, yet it is likely more energy-efficient than restricted movements. The enhanced range of motion observed in apes and early humans has been advantageous throughout evolution and remains beneficial for humans to this day.
Overall, this groundbreaking study sheds light on the significance of flexible shoulders and elbows in the evolutionary history of apes and early humans. It offers valuable insights into how our ancestors navigated trees and explains why apes possess greater flexibility in these joints. The findings underscore the importance of this adaptability throughout our evolutionary journey.
“Zombie enthusiast. Subtly charming travel practitioner. Webaholic. Internet expert.”