The rotating shoulders and extending elbows that allow humans to reach for a high shelf or toss a ball with friends may have first evolved as a natural braking system for our primate ancestors who simply needed to get out of trees without dying.
Dartmouth researchers report that apes and early humans likely evolved free-moving shoulders and flexible elbows to slow their descent from trees as gravity pulled on their heavier bodies. The paper, “Downclimbing and the evolution of ape forelimb morphologies,” is published in Royal Society Open Science.
When early humans left forests for the grassy savanna, the researchers say, their versatile appendages were essential for gathering food and deploying tools for hunting and defense.
The researchers used sports-analysis and statistical software to compare videos and still-frames they took of chimpanzees and small monkeys called mangabeys climbing in the wild.
They found that chimps and mangabeys scaled trees similarly, with shoulders and elbows mostly bent close to the body. When climbing down, however, chimpanzees extended their arms above their heads to hold onto branches like a person going down a ladder as their greater weight pulled them downward rump-first.
2023-09-06 06:48:03
Source from phys.org