Some Generous Apes May Help Explain The Evolution Of Human Kindness

It's feeding time at Lola ya Bonobo, a sanctuary for bonobos in the Democratic Republic of the Congo.

"Allez," caretaker Bernard Nsangu shouts in French as he gets ready to distribute a morning snack. The air fills with piercing shrieks as bonobos nearby tell their friends in the forest that pineapple is coming.

Soon, more than a dozen bonobos have assembled near the grassy perimeter of their enclosure.

With chimpanzees, the prospect of food can lead to aggression.

But bonobos take a different approach, says Suzy Kwetuenda, a biologist at Lola, for whom English is a third language. "As you see, there is many action of sex, many negotiation," she tells me. "So that make peace."

This sort of harmony is why, for more than a decade, scientists from around the world have been coming to this sanctuary just outside Kinshasa, along the banks of the Lukaya River. The researchers think bonobos may help explain how humans evolved the capacity to be nice – at least some of the time.

Same genes, different behavior

Bonobos look like smallish chimpanzees, with whom they share 99.6% of their DNA. And both of these great apes share 98.7% of their DNA with humans, making them our closest living relatives.

What intrigues scientists is that bonobos and chimps often behave very differently, despite their genetic similarity. What's more, human behavior seems to incorporate aspects of both species.

For example, chimps tend to rely on cunning and competition, while bonobos emphasize cooperation and sharing. The two species also diverge when it comes to leadership, says Dr. Jonas Mukamba, the head veterinarian at Lola.

"Chez bonobo," he tells me, "it is the females who dominate and it is a female who is chief of the group."

That's one reason meals at Lola ya Bonobo are so peaceful, Kwetuenda tells me as we watch a group of bonobos gather for what will soon turn into a sort of polyamorous picnic.

She points to the alpha female. "This is Semendua, big mom, tough mom," she says. "And as you can see she is in the front just to show that she is very concerned by all organization in the group."

Semendua is smaller than many of the males around her. But if a male were to become aggressive, all the females would rally around her to chase him into the forest.

Sharing with strangers

One way that bonobos differ from other great apes is in their eagerness to share, something that has been documented in a series of experiments here at Lola.

The experiments were carried out by a team that included Kwetuenda and Brian Hare, a professor of evolutionary anthropology at Duke University. They were done in Lola's "bonobo lab," a building that features room-size cages and a place for scientists to observe what happens inside them.

In one experiment, the scientists put two bonobos in adjacent rooms. Then they gave one of the animals a plate of prized food, like bananas or apples, which have to be imported. The fruit plate was topped with a type of cream Kwetuenda calls "bonobo sauce."

The bonobo with food was given a choice: eat alone, or use a special key to let in their neighbor.

"In our mind, we thought that because of nice food they would first eat," Kwetuenda says. "But we were surprised to see that roommate is more important than favorite food."

Later, the scientists repeated the experiment with three bonobos, one of whom was a stranger. This time, the bonobo with food usually shared with the stranger first, then invited the friend to join in.

In another study, scientists showed that bonobos are willing to help one another obtain food even if they know they won't get to share it. This generosity with food does not extend to tools, though.

Apparently selfless behavior may seem odd from an evolutionary perspective. But scientists believe it paved the way to the sort of large-scale cooperation that has helped Homo sapiens outlast other early humans, like Homo erectus. And this sort of cooperation has allowed our species to share new ideas, create vast nations and explore other planets.

A lab in the forest

Research at Lola ya Bonobo has produced more than 75 published studies. Scientists keep returning because the DRC is the only place on earth where these animals still live in the wild, and this sanctuary provides a unique place to study their behavior in a naturalistic setting.

Lola was founded nearly 30 years ago by Claudine André, a Belgian whose father was a veterinarian in Kinshasa. In 1991, while working at the Kinshasa Zoo, André looked into the eyes of a bonobo and, she says, "fell in love with this species."

After Lola moved into its current home (once a summer residence for former president Mobutu Sese Seko), André began hosting scientists from countries including the U.S., Japan and Germany. Over the years, scientific research has been able to document many of the bonobo behaviors that André and the Lola staff see every day.

For example, André has often said that bonobos are "full of empathy." And sure enough, an Italian team found that if one bonobo yawns, others will yawn too — a behavior closely associated with empathy.

Research also support André's belief that bonobos have a keen understanding of what's going on in another individual's mind, and when that individual wants to help them.

In their book Survival of the Friendliest, published in 2020, Brian Hare and Vanessa Woods describe an experiment in which a researcher would hide a treat under one of two upside-down cups. Then they invited several different animal species to figure out which cup hid the treat.

Chimps, despite their cleverness, just kept choosing one of the cups at random. But bonobos (and dogs) almost immediately learned to look to the scientist for a gesture indicating the right cup.

One study even found a structural difference between the brains of bonobos and chimps. The difference involved circuits controlling social and emotional behaviors.

What all the science suggests is that bonobos have evolved in a way that predisposes them to sharing, tolerance, negotiation and cooperation.

Those are all traits you can see in humans, on a good day, André says.

"Humans can be a fantastic bonobo with a big heart or a very dangerous warrior," she says. "We are mixed."

Lessons from a close relative

It's been about 6 million years since the death of the last common ancestor we shared with chimps and bonobos. Since then, we humans have channeled our inner bonobo to share and cooperate on a massive scale.

But we've often acted more like chimps — whose murder rate in the wild is comparable to our own — when it comes to behaviors like violence against members of our own species.

Humans do not share bonobos' assumption that every stranger is a potential friend. Studies show we may not even consider a stranger fully human if they belong to a group perceived as other and threatening.

When that happens, scientists say, we tend to suppress empathy and embrace cruelty.

Human cruelty is something Yvonne Vela Tona, a caretaker at Lola ya Bonobo, has seen up close.

Vela Tona fled Angola more than 20 years ago to escape a civil war that would eventually kill more than 500,000 people. Since then, she's lived in the DRC, a nation where decades of armed conflict has led to millions of deaths.

Vela Tona has raised children of her own and served as a surrogate mother to more than 20 bonobos. She's seen both the chimp and bonobo sides of human behavior.

What people can learn from bonobos, she tells me through an interpreter, is that war and violence are not inevitable, that we, like bonobos, have the capacity to resolve conflicts through other means. [Copyright 2021 NPR]