"What was surprising in our study was that the number of very close friends - the ones people interact with as much as family and exchange information - was on average the same, three to five, in both Congo and the Philippines in all age groups," Migliano said. She added that this average number of very close friends is mirrored in Westernized societies.
Without computers, social media or even telephones, hunter-gatherers have social networks that are nearly identical to those of modern urban populations. The paths to those networks may be very different, but the end results are about the same.
The researchers have not mapped the social networks of other primates yet, but earlier research suggests that chimpanzees and other primates tend to form close alliances with relatives and do form friendships, but Migliano said they "have fewer opportunities to befriend unrelated individuals, and cooperation between unrelated individuals is much less frequent."
As a result, non-human primates have smaller social networks and a limited ability to learn innovations developed outside of their tight spheres.
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In Western societies, close friendships often form in school. For hunter-gatherers, such alliances usually are forged in "playgroups." Migliano said these "are like a school, where children are learning through play, imitating each other, and creating the foundations of their future social networks."
The take-home lesson from these and other studies is that investing in a few good friends from different families can make social networks more efficient.
"Based on that, it seems that the recipe for good social networking is to avoid two extremes: being too cosmopolitan - trying to know everybody and everywhere, but only superficially - or too provincial by not extending your links beyond family or local ties," Migliano said.
As for the hunter-gatherer study participants, they were not interested in keeping the mote devices. Instead, at the end of the research period, they and their family members received some coveted Thermoses and cookware.
Top photo: Child friendships from the BaYaka hunter-gatherer tribe. Credit: Timothy Allen/Getty Images