Generosity can be contagious, suggests new study

At first glance, being generous does not really make sense. From the point of view of evolution, it may seem that being selfish is the best idea. But for a social creature like Homo sapiens, things are rarely simple and recent studies suggest that generous people are happier and more successful in society. But that still does not explain Why we give.

This is where the new study comes in. The researchers found that the Hadza, a hunter-gatherer people, are usually willing to share – but that does not mean they always do. In fact, the fact that they are willing to share something depends not only on the individual, but rather on the group with which they lived at the time.

"We have seen year by year the willingness to share with other groups grouped into residency groups or what we call" camps, "says lead author Coren Apicella of the University of Toronto. Pennsylvania. "People lived with others who looked like them by their level of generosity."

In other words, people were more generous when they were in the company of other generous people – not the other way around.

"We also found that the individual willingness to share with members of their camp rose from year to year and found no evidence that people preferred to live with more cooperative people," adds Kristopher Smith, the first author of the study. Importantly, these trends persisted even though the Hadza changed sides every two months or so.

Hadza, or Hadzabe, is an indigenous ethnic group in north-central Tanzania, near the Serengeti Plateau. In 2015, there were between 1,200 and 1,300 Hadza living in Tanzania, although the increasing impact of tourism and the encroachment of pastoralists seriously threaten the continuation of their traditional way of life.

Studies like this are particularly important because they have been conducted on a society that is very similar to a subsistence lifestyle similar to most human developments. Plus, as they earn most of their calories from hunting and plant gathering, both resources that are quite rare, sharing are really generous – not something to be treated lightly.

"The Hadza are one of the last populations on the planet to live a lifestyle similar to that of our ancestors for millions of years," says co-author Ibrahim Mabulla. "They offer insight into the evolution of cooperation."

"The food is not reliable and people often worry that there is enough food to feed themselves and their families," Apicella says. "To counter this, the Hadza share their food with their campmates. High levels of cooperation help ensure survival in this unpredictable context.

The methodology of the study was almost as interesting as the study itself. Obviously, it is not easy to study this type of population, especially since researchers have taken special care not to disturb them significantly. Thus, to test their theories, researchers visited 56 camps in Tanzania for six years.

During these visits, nearly 400 adults of all ages were invited to play a game of public goods. The game is normally played by asking people to decide whether they share money with the group or to keep it for themselves – but as it would not make much sense here, money has been replaced by straws of honey, the favorite dish of Hadza.

In the game, each person starts with four straws. If they decide to keep them, they keep them. But if they share them with the group, they tripled. If everyone shares, everyone wins – but there is also an incentive to keep straw for you.

Data showed that Hadza individuals living in some camps were consistently more generous than others. In addition, individuals have behaved differently over time, changing their behavior to match the norms of the camp in which they currently live.

"You have camps in which everyone contributes and others where people contribute very little," says Smith. "In a random population, you expect all the camps to bring in similar amounts."

"We were surprised to find that people do not have a steady tendency to cooperate and that they are rather influenced by those around them," says Apicella. "Our results show that there are no good guys and bad guys," challenging a series of evolutionary models to explain cooperation that involves dispositional types: co-operators and defectors.

Finally, it also shows the fluid nature of human collaboration – it can evolve over time and be influenced.

So, if you feel that the people around you are selfish and selfish, the best way to change that is to start being more generous – who knows, you could give them the contagion of generosity.

Journal reference: Current Biology, Smith et al.: "Hunter-gatherers maintain assortment in cooperation despite high levels of change and mixing in the residential sector" https://www.cell.com/current-biology/fulltext/S0960-9822(18) 30994-1

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