Which animal is man's best friend?

Look into my eyes! : How the dog became man's best friend

Such a thing would never occur to a wolf, not even if it was raised by humans: A long look into the eyes of the person opposite is not a sign of special affection for these animals, but rather a threat. When the dog became man's companion over the millennia, that must have changed at some point. Because eye contact now enables deep friendship across species boundaries, report Takefumi Kikusui from Azabu University in Sagamihara, Japan, and his colleagues in the journal "Science". Both sides can strengthen the bond thanks to the hormone oxytocin. Among other things, oxytocin plays an important role in the relationship between mother and child in mammals.

Oxytocin sprayed in the nose

In their experiments, the researchers initially documented all interactions between dogs and their owners for half an hour. The longer they looked each other in the eye, the more oxytocin was later to be found in their urine. In a second experiment, the researchers sprayed oxytocin into the noses of some dogs and then let them with their owners. This time it was mainly females who sought eye contact with their human counterparts. And this could not escape: After 30 minutes, the oxytocin concentration in the urine of the person had risen. Eye contact strengthens the bond on both sides.

"I'm not surprised," says Roman Wittig from the Max Planck Institute for Evolutionary Anthropology in Leipzig. Because beyond eye contact, there is one more thing in common: the owner feeds his dog and the mother breastfeeds her baby. It has been known since the beginning of the 20th century that the mother releases larger amounts of this hormone during childbirth and when breastfeeding. First of all, oxytocin ensures that the placenta is rejected in the afterbirth. At the same time, the substance binds to certain receptors in the brain as a messenger substance and thus supports the first contact between mother and child. This bond is confirmed and strengthened again and again during breastfeeding - and not just in humans, but in all mammals that researchers have previously examined for oxytocin. You call it positive feedback.

The chemical message can create friendships

The hormone also helps animals and humans to establish friendships: “In nature, chimpanzees sometimes share their food with other group members,” observed Wittig on the Ivory Coast. Because researchers cannot directly measure the release of oxytocin in the brain in nature, they instead determine the hormone content in the urine, because it rises or falls at the same time. "About thirty minutes after one of the chimpanzees has shared its food with another in his group, the oxytocin concentration in the urine increases fivefold," says Wittig. Even if the chimpanzees are not yet friends. So the chemical message can create friendships. By contrast, existing relationships are more likely to be confirmed through grooming, as shown by comparative oxytocin measurements.

Apparently the relationship between master and dog works in a similar way. In any case, the four-legged friends enjoy being petted. If the two-legged friend regularly serves food, he ties the ties a little closer. The dogs owe the fact that we take such care of them, among other things, to the look in the eyes, which is unusual for mammals. Presumably, it was above all those animals who sneaked into the hearts of people (and breeders) who sought eye contact out of a coincidental whim of nature.

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