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homo have ape antecedent to thank for their flexible shoulder and elbows , which may have evolved as a rude braking mechanics for tree diagram - grading .
Scientists made the find while follow legion video ofchimpanzees(Pan troglodytes ) and sooty mangabey ( Cercocebus atys ) monkeys , which are much more distantly related to to both chimp and humans , go up up and down trees in the natural state .
A chimpanzee uses its flexible shoulders and elbows to brake as it descends a tree.
In the new subject , the researchers noticed that although both animals ascend trees similarly with their shoulders and elbow tight bent toward their bodies as they fleetly reached from one ramification to the next , they differ in their techniques for descending .
The finding suggest that chimps and human being may have pliable shoulder and cubital joint joints as a fashion to " counteract " the effect of gravity on their threatening small bodies . The result was a finely calibrate braking system of rules that lessen their risk of infection of fall while they descended downward high up in the treetops , fit in to the study , release Sept. 6 in the journalRoyal Society Open Science .
While mangabeys were less conciliatory , the chimps extended their weapons system above their heads while fall — interchangeable to the direction a person goes down a ladder . This maneuver was a way of life for the primates to slow their descents asgravitypulled them downward , the team said in astatement .
" [ We ] noticed that while both chimp and mangabey climbed tree in a clipped motility where they did n’t amply protract their joints , in downclimbing the mangabey continued this clip motion , while the chimp did not , " co - author Mary Joy , a biological anthropology major who graduated from Dartmouth University in 2021 and made this her undergraduate dissertation , tell Live Science . " The two had very dissimilar ranges of move . "
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Human and chimpanzee ancestorsdiverged approximately 6 million to 7 million years ago , while the mangabey ’s monkey ancestordiverged from apes around 30 million long time ago .
But the field suggests that pliant appendages had germinate by the sentence of the last common ancestor between chimps and humans , but after apes and monkeys diverge . This flexibleness would have leaven good for thing that involved specific movements like gather nutrient , hunting and defending themselves , according to the study .
This marks the first time investigator have extensively canvas how with child apes descended trees ; antecedently , most study were focused on them climbing .
" We knew generally that Pan troglodytes had an increased orbit of movement in their shoulder and elbows , while mangabey did not , " Joy say .
This is because mangabey and other monkeys are work up similarly to four-footed mammal like cats and bounder , which take the air on all quaternary and have " cryptic , pear - mould shoulder sockets , " the team said in the statement . The intimate outlaw of their elbow joint also come out , making the joint resemble the letter " L , " concord to the affirmation . These joints may offer stability , but they lack a good range of gesture .
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Upon analyzing the joints in existing chimp skeletons that were part of museum collections , researchers noticed that the angle of the apes ' shoulders was 14 degree expectant when they were descending versus when they were climb . Their arm also extended outward at the elbow 34 stage more when the Pan troglodytes were run down trees , according to the cogitation .
This modification in movement not only help oneself the chimps slow the pull of gravity but also allowed them to decelerate safely .
" Chimps can get out of tree and climb downwardly without have to keep their shoulder and cubitus muscles under tension , which leave in the exertion of a lot of get-up-and-go , " Joy said . " As humans , the introduction of this increased range of move had a lot of benefit , like lease us elevate our blazonry above our heads or throwing a egg . This question is a legacy ofevolutionarypressure on our ancestors , which gave us the power to do a lot of things . "
