January 26, 2012

Ancient Tanzania Had Early Social Network

Who´d have thought Facebook was popular in an ancient Tanzania culture? Well it wasn´t, but the people of the Hadza group exhibited many of the “friending” habits familiar to today´s Facebook users, suggesting that social networking patterns were set early in the history of our species.

While ancient humans didn´t have the luxury of updating their social status, social networks were indeed an essential part of their livelihood, say authors of a new study, published in the journal Nature.

Findings of the study showed basic social network structures may have been present early on in human history, suggesting that our ancestors may have formed ties with both kin and non-kin based on shared attributes, including the tendency to cooperate. Researchers in the study believe social networking likely contributed to the evolution of cooperation.

The team mapped out the relationships among the remote Hadza group of 205 hunter-gatherers in Tanzania who still live just as humans did 10,000 years ago. What they found was that the group´s social networks are very similar to ours, minus smartphones and the Internet of course.

“The astonishing thing is that ancient human social networks so very much resemble what we see today,” said Nicholas Christakis, professor of medical sociology and medicine at Harvard Medical School and professor of sociology in the Harvard Faculty of Arts and Sciences, and a senior author of the study. “From the time we were around campfires and had words floating through the air, to today when we have digital packets floating through the ether, we´ve made networks of basically the same kind.”

“We found that what modern people are doing with online social networks is what we´ve always done -- not just before Facebook, but before agriculture,” added study co-author James Fowler, professor of medical genetics and political science at the University of California, San Diego.

The study findings offer plausible answers to why humans cooperate with one another.

Natural selection might dictate that free riders in a community -- selfish individuals who take advantage of other people´s generosity -- would out-compete their more selfless brethren. But social networks may have been useful in making sure that cooperative individuals were able to work together successfully.

Recent studies linking genetic variation to social network structure lent further credibility to the notion that social networks may have evolved for survival purposes. For example: scientists have found evidence that social networks of identical twins are more similar than those of fraternal twins, suggesting that genes play a role in such areas.

“If these properties are written in our genes, is this something we would find in humans who lived like we would have lived thousands of years ago?” asked Fowler.

Harvard Medical School researcher Coren Apicella may have the answer.

Apicella traveled to the remote regions of Tanzania to study members of the Hadza group. The Hadza live just as ancient humans did in the Pleistocene: no agriculture, few possessions, setting up camps only to hunt and forage, and relocating every four to six weeks after stripping the bushes and baobab trees within walking distance.

“They provide a kind of window into the past,” said Christakis.

The Hadza travel in wandering bands spread out around Lake Eyasi. If individuals do not like the bands they are in, they can leave and go join another one, which sets up an interesting opportunity for the researchers to investigate the groups´ social network.

“If you can get cooperators to cluster together in social space, cooperation can evolve,” said Apicella, lead author of the study. “Social networks allow this to happen.”

Apicella showed 17 different Hadza bands a primitive version of Facebook -- a printout with head shots of all the Hadza in all the bands -- and asked them to identify who they would like to be with in the next band they joined. Apicella showed the men in the bands only men´s headshots, and women only women´s headshots, so that romantic aspirations would not complicate the results.

The Hadza were also given three sticks of honey, a prized possession in their cultural communities, and asked to choose three people to whom they would give each honey stick. The tests enabled the researchers to map out the Hadza´s social networks.

In a third experiment, four honey sticks were given to each of the Hadza. They were told they keep all four for themselves, but were also told that each stick they anonymously contributed to a common pile would be tripled by the researchers and redistributed later on.

This test was used to see which individuals were more cooperative and which were free riders, opting to secretly keep their sticks while also benefiting from the redistribution of sticks in the common pile.

After compiling their data, the research team found that Hadza who contributed more to the common pile were more likely to be friends with other cooperative people. These connections formed clusters that were mostly near the center of the social networks. This made the group more successful and better able to compete with other groups for resources, said Christakis.

“If you can get cooperators to cluster together in social space, cooperation can evolve,” said Apicella. “Social networks allow this to happen.”

The structure and dynamics of the Hadza hunter-gatherer social networks were essentially indistinguishable from existing social network data gathered from modern communities.

“We turned the data over lots of different ways,” Fowler told the Los Angeles Times in a news release. “We looked at over a dozen measures that social network analysts use to compare networks, and pretty much, the Hadza are like us.”

“Human beings are unusual among species in the extent to which we form long-term, non-reproductive unions with other members of our species,” added Christakis. “In other words, not only do we have sex, but we also have friends.”

In compiling the data from the study, the researchers were surprised to find that the free riders were more likely to be friends with other free riders in the groups. The team thinks this is so because those who tend to cooperate choose to be friends with people like themselves, leaving no space for free riders.

It could also have to do with the possibility that free riders actively prefer the company of other free riders because they are less likely to be criticized of their behavior, said Joseph Henrich, an evolutionary researcher at the University of British Columbia in Vancouver who was not involved in the study.

He said this study provides a “glimpse into the social dynamics of one of the few remaining populations of nomadic hunter-gatherers.”

Fowler acknowledged, however, that studying hunter-gatherer societies are not a foolproof way to trace the evolutionary roots of the behaviors we see in modern-day society, including Facebook friending and Twitter tweeting.

“This isn´t necessarily the be-all and end-all of determining what we were like hundreds of thousands of years ago,” he said. But considering that scientists can´t interview Stone Age social networkers, Fowler believes this is one of the best methods available to anthropologists.

Apicella collected the raw data for the study, and designed the study and experiments along with Fowler and Christakis. The team worked with Frank Marlowe, lecturer in the Department of Archaeology and Anthropology of the University of Cambridge, and author of the only book-length ethnography on the Hadza in English.

Data collection proved to be quite difficult for Apicella and her colleagues. The Hadza roam an area of 2,500 rugged square miles, leaving the team to travel by Land Cruiser, battling mud-drenched trails and hordes of animals -- at one point having to flee a horde of stampeding elephants.

The Hadza offered the researchers strong new evidence that social networks are a truly ancient, perhaps integral part of human life.


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