If this blog were Us magazine, we'd say: Hunter-gatherers, we're just like them.

Because seriously, we are.

Here's the story. Humans today live and work in communities with vast numbers of folks we're not related to.

And we often quite happily cooperate and share knowledge with strangers or mere acquaintances. These exchanges allow us to innovate and develop increasingly complex technologies.

And that cooperative behavior, which is fairly unique to humans, may be rooted in the fact that our hunter-gatherer ancestors believed that women and men were equal!

That's the upshot of a new study published this week in Science. A team of anthropologists at University College London interviewed hundreds of couples in two hunter-gatherer tribes, the Palanan Agta of the Philippines and Congo's Mbendjele BaYaka, as well as the Filipino farming tribe the Paranan, which is a patriarchal society.

Of course, contemporary tribes don't necessarily live the way their forefathers and foremothers did. They "are not living fossils," explains Mark Dyble, the doctoral student who is the study's lead author. But they do likely offer anthropologists a strong approximation of the lifestyles and communities of our oldest ancestors. And the way we behave today largely evolved from the successful strategies that our progenitors adopted to survive.

So how did gender equality perhaps lead to humans learning the benefits of helping and working with strangers? It all comes down to housing.

Members of current hunter-gatherer tribes say they prefer to live close to their kinfolk. That makes sense, since siblings and grandparents can help with child care.

But even though that's what they say, it's not what they do. In fact, the tribes live in camps that are heavily populated with folks to whom they're not related.

That anomaly has long been noted by researchers, but it remained an unsolved puzzle. "Now we have an explanation for why that is," Dyble says.

Here's what his team found.

Hunter-gatherer tribes today live in groups of 10 to 50 households, with an average of about 20. The composition of each group changes almost constantly, which is not surprising given that households tend to move every 10 days or so as they hunt and gather.

In a patriarchal society, the men make all the decisions about which group to join — and these couples do end up living in villages mostly composed of the husband's relatives.

But men and women in hunting-and-gathering tribes have an equal say in deciding which groups they'll join. (That kind of gender equality reflects the important role both parents play in raising children.)

Usually, the wife wants to live with her people and the husband wants to live with his people. So the spouses are constantly trying to accommodate each other. But when all of a tribe's households are trying to put together camps mostly inhabited by kin and in-laws, you can imagine how complicated the negotiations get. And so in the end, neither husband nor wife succeeds in creating a family camp.

"It is not that individuals are not interested in living with kin," says Dyble. "Rather, if all individuals seek to live with as many kin as possible, no one ends up living with many kin at all."

What's surprising here is that even though these people end up living with a bunch of strangers, the group members cooperate. They readily share resources, and they hunt, fish and collect food cooperatively, despite the lack of blood ties. Why?

"Sharing and cooperation is crucial to survival," explains Andrea Migliano, the paper's senior author. "So [tribe members] evolved mechanisms to cooperate with unrelated individuals."

Researchers visited this Mbendjele camp in a forest in the Republic of Congo to talk to hunter-gatherers.

Researchers visited this Mbendjele camp in a forest in the Republic of Congo to talk to hunter-gatherers.

Nikhil Chaudhary/Courtesy of University College London

For example, hunters only find food about 75 percent of the time. That would mean a family would go hungry one day out of four. But that doesn't happen because unrelated neighbors learned to share their food.

It turns out there's another benefit to reducing the number of kinfolk in a camp. The result is that any given individual would probably have a relative or two in lots of other camps. And those family ties make it easier for different camps to bond with each other and exchange information and tools instead of trying to buy or take stuff by force.

The equal rights attitude of the hunter-gatherers didn't survive when these folks turned to farming. Patriarchal lines took precedence for passing down land, and gender equality went out the door.

But the strategies for getting along with strangers have stayed with us.

So if you wonder why, despite the ability of humans to be warlike and cruel, we can also donate blood to strangers and write checks to charities that help people we don't know ... maybe it's the legacy of our hunter-gatherer past.

Copyright 2015 NPR. To see more, visit http://www.npr.org/.

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