One German investigator spoke of an Orgasmusgesicht (orgasm face) given by females while they stare into their partner’s face. Bonobos, who often mate face to face, sometimes bare their teeth in friendly and pleasurable situations, such as during sexual intercourse. In many ways, their expressions and the way they use them are more like ours. The great apes go a step further: Their grin, although still a nervous signal, is more positive. Hence, Orange received the signal many times a day, whereas a snake never would. The same applies to the monkey grin: It expresses a desire for good relations. No one would mistake the canine rollover for an act of fear because dogs often behave this way while approaching the other as an opening move. He exposes his belly and throat while trusting that you will not use weaponry on his most vulnerable body parts. It is a bit like the way a dog may greet you, with flattened ears and tucked-in tail, while rolling on his back and whining.

The grin, though, is an intensely social signal that mixes fear with a desire for acceptance. When a monkey is simply scared, such as when it spots a snake or predator, it freezes to avoid detection or else it runs away as fast as possible. However, far more underlies this expression than fear.

But the original primate signal to make clear that you rank below someone else is a grin with the mouth corners pulled back. Chimpanzees lower themselves in the presence of high-ranking individuals and issue a special kind of grunt to greet them. Humans signal subordination by bowing, groveling, laughing at the boss’s jokes, kissing the don’s ring, saluting and so on. Every species has signals for this purpose, though. As such, it is an unambiguous marker of the hierarchy. None of them moved out of her way, but the expression told her, “I’m subordinate, I’d never dare challenge you.” Orange was so secure in her position that she rarely needed to use force, and by showing their teeth, the other females removed any reason she might have had for throwing her weight around.Īmong rhesus monkeys like Orange and her troop, this expression is 100 percent unidirectional: It is given by the subordinate to the dominant, never the other way around. All the females she passed would flash her grins - especially if she walked in their direction, and even more so if she honored their huddle by joining them. In a rhesus monkey group at the Vilas Park Zoo in Madison, Wisconsin - where I studied as a primatologist - the mighty alpha female, Orange, needed only to walk around to evoke the expression from others in her troop. Films of people riding roller coasters often show not delighted smiles but terrified grimaces. I’ve observed baboons grinning to avoid perforating their lips while eating a succulent cactus.įear and unease also pull at the corners of our mouths. For example, when we peel a citrus fruit - an action that risks spraying drops of acidic juice into our face - we automatically pull our lips back from our teeth. The grin, it seems, derives from a defensive reflex. Our hands came from the forelimbs of land vertebrates, which derived from the pectoral fins of fish. The latter question may seem odd, but everything in nature is a modification of something older. Many questions surround the grin, such as how this toothy expression became a friendly one in our species and where it came from. The row of bright white teeth makes it a conspicuous signal, visible from far away, yet its meaning is the exact opposite of a threat. In a grin, the mouth is closed, but the lips are retracted to expose the teeth and gums. That fierce face, which looks like an intention to bite, acts as a threat. The bared-teeth grin is not to be confused with a wide-open mouth and intense staring eyes. Behind the scenes, a trainer is waving his electric cattle prod or leather whip to make clear what will happen if the animals fail to obey. It’s hard to get these animals to bare their teeth without scaring them - only punishment and domination can call forth these expressions. People may think they’re hilarious, but I know their mood is the opposite of happy. Every time I see a dressed-up simian actor produce one of their silly grins, I cringe. I can’t stand TV sitcoms and Hollywood movies featuring monkeys and apes.

Picture of a chimpanzee smiling