chimpanzeeschimpanzeesJust like humans, chimps bond with a little help from their hormones. (Photo: Sergey Uryadnikov/Shutterstock)

Cliques are way more ancient than we thought

In a new study, scientists identify the hormone that makes chimps band together in times of trouble.

Has your clique ever teamed up to make sure uncool people don't sit at your lunch table? If so, you're not alone. Humans from around the world bond over being part of a group that's wary of outsiders. Recently, scientists set out to find the chemistry behind this behavior ... in chimpanzees.

A group of scientists from Germany's Max Planck Institute for Evolutionary Anthropology who studied chimpanzees in the wild, examined a lot of chimp urine samples (like, a LOT of urine samples). In particular, they looked at levels of oxytocin, a hormone often connected to trust, bonding and cooperation in humans and other animals.

The scientists discovered that oxytocin spiked when chimps were feuding with chimps from other tribes.

"We found high urinary oxytocin levels in hunting and intergroup conflict," explained Israeli scientist Liran Samuni, a Tel Aviv University graduate who headed the study. "Both contexts involve group coordination."

Researcher Liran Samuni Researcher Liran Samuni

"The chimpanzees' hormone levels were significantly higher than in contexts without coordinated group activity and were not affected by potential threat or in-group affiliative interactions. However, given that intergroup conflict showed significantly higher levels than all other examined events, we concluded that the observed effect is reinforced in the context of in-group out-group perception," Samuni continued.

The scientists thought oxytocin helped the chimps band together, creating a stronger group to ward off harmful outsiders.

"Chimpanzees are like a band of brothers in the Shakespearean spirit of Henry the Fifth's St. Crispin day speech," said Roman Wittig, a scientist from the Max Planck Institute for Evolutionary Anthropology who worked on the study. "In the face of a rival group, chimpanzees' social bonds allow them to stand by each other."

Along with bonobos, chimpanzees are our closest relatives. We share 99 percent of our DNA with these great apes (technically, we're great apes too – spectacular apes, in our opinion) as well as a great-great-great-great-great (throw in as many greats as you can here) grandparents. Some scientists even think great apes could probably raise human children, if need be. So there's a good chance our ingroup-outgroup behavior is no recent phenomenon – our ancestors have probably been doing it for quite some time.

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