Chimp non-kin relationship study
Researchers have revealed that a particular hormone causes chimpanzees to bond socially with non-relatives, even when outside of a sexual relationship.
A team of international scientists conducted the study using wild chimps in Uganda. They tested each of the chimp's urine after grooming sessions with both "bond-partners" and "non-bond partners" in order to make their discovery.
The urine revealed that those chimps taking part in grooming session with a bond partner had a higher level of the hormone oxytocin in their urine afterwards, compared to those grooming non-bond partners.
Before now, oxytocin had not been associated with non-kin relationships, as it is usually implicated in mother-baby and pair bonds. Previous studies, however, have shown that animals that can maintain cooperative relationships have greater life expectancies and produce healthier offspring.
Catherine Crockford, a member of the research team, from the Max Planck Institute for Evolutionary Anthroplogy in Germany, compared non-kin relationships in the animal kingdom to human friendships.
"Even though people are not related to each other and they're not in a sexual relationship where they could produce offspring, they still co-operate," she commented. "And nobody really has a good explanation for how this can happen."
Dr Crockford added that tactile stimulation, such as gentle stroking, was previously thought to be enough to stimulate oxytocin.
"But this clearly shows that's not the case... you need more than just that," she said. "There needs to be some sort of psychological component really, this added factor of the relationship itself and the quality of the relationship."
The results have been published in the journal Proceedings of the Royal Society B.
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