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It is not just a matter of physical appearance: we share with the other great apes (orangutan, gorilla, chimpanzee, bonobo) at least 97% of our genetic code, and with them, and other primates, an unexpected range of expressions, reactions, behaviors and social interactions. Here is a selection of these behaviors, chosen among the least known.

They ask for food with their hand. Chimpanzees ask for food with an open, stretched hand, just like humans. They often accompany the gesture, leaving the exposed teeth visible, with an expression that is difficult to resist. The mandrills of a British zoo have instead been seen to cover the face with a paw whenever they wish to be left alone (a sort of "do not disturb"). Discoveries of this type seem to indicate a birth of gestural communication as a shared language before the advent of verbal communication.

They say "no" shaking their heads. Some bonobos (Pan paniscus) from the Leipzig zoo were observed shaking their heads disgruntled in front of the puppet pranks: they made the gesture when the little ones played with food instead of eating, or when they went too far despite maternal attempts to bring them back to himself. We do not know if the "no" of these monkeys has the same meaning as ours, but the attitude is also common among chimpanzees: in their case, the shaking of head was associated with the attempt by the females not to let the puppies get closer to angry and aggressive males. The gesture that corresponds to the denial could have been born in a common ancestor to man and apes.

They recognize faces. Human beings are apt to recognize the smallest differences in the faces of their fellows - even when their faces are scattered among many others. So the monkeys: researchers at the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, verified it by subjecting some macaques to a classic test in which the features of the face are slightly distorted (for example, by rotating eyes or mouth 180 degrees ). Just like the man, the macaques noticed the anomalies in the distorted faces of their peers when they were presented in the right direction (eyes up and mouth down), but they didn't notice when the faces were turned upside down. This happens because the faces are coded, perceived and memorized according to a "classic" orientation and in their entirety (rather than in several broken elements).

They laugh with taste. Especially in a situation where nobody can do without it: tickling attacks. The laughter of the great apes is darker than the human ones, but the alternation of sounds and the expression they make are so similar to ours that even the experimenters are "infected" by the fun. A 2009 study, which compared the laughter of orangutans, gorillas, bonobos and chimpanzees during tickling to those of children, revealed that monkeys laugh by following our own mechanisms: they emit a shortness of breath, even if the conformation of their larynx does not allow the classic "ah-ah" of human laughter.
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They eat junk food to cheer themselves up. A stressful social life leads humans to console themselves with chips and ice cream, and in monkeys it doesn't work very differently. The female rhesus macaque (Macaca mulatta) who are in the lower ranks of the group hierarchies show visible signs of stress such as frequent yawning, itching, self-grooming and lack of appetite. When researchers at Emory University (Georgia) provided them and the monkeys with the highest possible fat and sugar rich diet, western macaques ate more "junk food" than those made . And unlike their "bosses", they continued to take crap even at night.
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They use sex toys. In the kit of about 20 different types of tools ("tools") that the chimpanzees of various populations have learned to use, there are some dedicated to improving their sexual life. They are "tools of pleasure" but in a slightly different sense from what we mean: the chimpanzee males of a Tanzanian population use dry leaves to attract the attention of females on their erection, and bring them closer to themselves. They sit well "in sight" and begin to smash the leaf into tiny pieces making noise and making sure their enthusiasm is noticed. If the females "catch", it comes forward and mates begin. 11 curious and historical facts about sex toys

They have "male" and "female" games. Even non-human primates seem to prefer games of different types based on the genus they belong to. Among humans, children's preferences for toy cars or dolls seem to be dictated by a mix of genetic predisposition and social influences. A 2008 experiment on 34 rhesus macaques in a population of 135 specimens showed that males preferred games with wheels, and females plushes: however, the latter, like human children, showed greater flexibility in the choice of favorite games. According to scientists, it is on these hormonal preferences that the generalizations we see also on humans are built.

They recognize unfair situations. "It's not fair! Why does he and me?": Protests of this kind are not just typically human. Also capable monkeys are not so close to us, such as the cebi from the croissants (Cebus apella): in an experiment, to these primates cucumber slices or the most loved grapes were offered in exchange for a piece of granite that had to deliver to the experimenters. When everyone had cucumbers, everything went smoothly. When the neighbors received the grapes, those who had the cucumber noticed injustice and went on a rampage: they threw the food on the ground and turned away, faced with the insistence of the scientists. The ability to recognize injustices is fundamental for the development of a cooperative society (in the photo, a macaque that is very attentive to what it receives).

They hatch revenge. Even the punishment of unjust and antisocial behavior seems to have correspondences between our "cousins". A recent study has shown that sapiens' children are willing to "pay" - symbolically - in order to see the villain punished in a puppet show. The same is true for chimpanzee adults: in order to see their thirst for justice satisfied, these primates are willing to offer something they own or make an extra muscular effort.

They make war. The two bonobos in the picture are having an aggressive interaction, but the primates closest to us are also capable of real wars, which can continue for years. The first was observed by the British ethologist Jane Goodall from 1974, between two populations of chimpanzees in the Gombe Stream National Park, in Tanzania, which previously formed only one. The war of the chimpanzees of the Gombe lasted until 1978, with repeated violent incursions of the one and the other group between killings, beatings, abductions and occupations. The awareness of this "dark side" in the behavior of chimpanzees left the scientist upset for a long time.

They kiss. Only the great apes (gorillas, orangutans, chimpanzees, bonobos) practice this intimate and sophisticated type of interaction. Usually they are kisses on the arms and on the chest, as a sign of respect and to strengthen social hierarchies. The chimpanzees - in the photo - kiss each other to cheer themselves up or to reconcile themselves after a conflict: it is a typically masculine gesture and without a sexual connotation. More "pushed" is the kiss between bonobos, which often involves the language: but bonobos are very explicit creatures in sexual behavior, and use very close interactions in a wide range of social situations: it is not the typically romantic kiss of man, but it is the closest thing in the world of primates.

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