Observing primates in the wild, one is often amazed at the way they they hover among the branches of the trees or they hang suspended with their fingertips. And it is no coincidence that the scientists who first studied the behavior of monkeys in the forest compared it to the performances of jugglers. But how did primates evolve this particular type of locomotion? And how have those anatomical structures evolved that allow the gibbons to swing from the branches and which today allow baseball champions to throw a ball or swing a bat?
A recent study, published in the journal, explains it Royal Society Open Science by a team of American biologists, which was led byUniversity of Hanover, in Dartmouth, New Hampshire. According to these scientists, in fact, this type of movement was made possible thanks to a series of particular adaptations that allowed the ancestors of modern primates to climb the tallest trees, without running the risk of falling to the ground.
The evolution of free shoulders and flexible elbows, facing outwards, first of all allowed primates to obtain a certain safety when falling, as it allowed the animals to reach out their arms and grab anything – from a vine, a branch or the outstretched arm of a partner – and to cushion or stop the fall. The anatomical structure of shoulders and elbows allowed monkeys to have some movement control while moving from one end of a tree to the other, going to execute precisely those maneuvers that limited the error.
Researchers have thus understood that both the shoulders and the elbows can be the “parachutes” of primates, being used even if these animals have to reach the ground very quickly. Going to carry out analyzes with statistical software usually used for evaluating player performance during matches, the scientists compared various videos and stills of chimpanzee and little monkeys called let it be or cercocebi died as they climbed.
The result was remarkable: while the two species scaled trees in a similar way, with shoulders and elbows mostly bent close to the body, when they descended they moved differently due to their weight difference and their goals. While the chimpanzees stretched their arms above their heads to cling to the branches, similar to how a human descends a ladder letting himself be guided by gravity downwards, the mangabe threw themselves right into the void, using their upper limbs to curb their falling speed. And in both cases the shoulders and the elbows were the main organs with which these species were able to control their descent.
“Our study believes that how primates descend from trees is an underestimated but incredibly important factor in the divergent evolutionary anatomical differences between species, which eventually manifested themselves in humans as well,” he said. Luke Fanninyoung first author of the study – Descent indeed represents such a significant physical challenge for these animals, given the size of apes and early humans, that their morphology would have responded through natural selection due to the risk of falls.
Without these organs, in fact, the primates probably would not have been able to conquer the forests nor to survive so long in the branches of the trees. “Given that the first apes evolved 20 million years ago in a type of scattered forest where it was essential to climb trees to get food, it is normal that even great apes cannot afford to fall, because it could kill or injure them. seriously – he clarified Jeremy DeSilvaprofessor of anthropology at Dartmouth – Natural selection would thus have favored those anatomies which allowed all primates, beyond their weight, to descend safely».
This would also have allowed later to develop particular articular movements, such as the swing of the gibbons, the long jump in humans and in some particular monkeys that leap from one tree to another, as well as also throwing objects in many sports and beyond.
To understand the importance of these two structures within our evolution, say the researchers, it is enough to consider the impact they had with the introduction of spears or bows. Without free shoulders and efficient elbows, we would not have been able to make the movements necessary to supply ourselves with food or to defend ourselves. Furthermore, if we observe the other mammals, we would notice that we are the only ones, together with the other primates and with a single exception, the koalas, to have equipped ourselves with these particular structures.
This is due to the fact that within our class, only we have adapted to live strictly within the foliage of the trees, the researchers explain. The other climbing mammals, such as bears or leopards, although capable of climbing, have never been frequent climbing enthusiasts. This has led them to develop adaptations more tied to dry land and not to evolve those descent techniques that allow them to land so safely.
2023-09-07 11:04:05
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