What a chimp’s emotions tell us about ours

Among ethologist Frans de Waal’s great gifts — and he has many — is one that makes his books so popular: his confidentially conversational tone. An original thinker, he seems to invite us to his front-row seats, sharing the popcorn as he gets us up to speed on the plot of how life works, through deeply affecting stories of primates and other animals, all dramas with great lessons for our own species.

De Waal, a professor at Emory University and director of the Living Links Center at the Yerkes National Primate Research Center, has spent his career immersed in research on animal behavior, cognition, morality, aggression, and the place of humans in this continuum. His latest and best book — a followup to 2016’s “Are We Smart Enough to Know How Smart Animals Are?” — takes a deep dive into the emotional lives of animals. Though science has long resisted the idea that non-human animals share aspects of human traits, de Waal brilliantly builds his case that emotions are “bodily expressed,” therefore somewhat measurable, and that not only can we see that other creatures have emotional lives, but that they can help us understand what underlies our own.

The first chapter of “Mama’s Last Hug: Animal Emotions and What They Tell Us About Ourselves,” begins, of course, with Mama, a chimpanzee in her late 50s, very old age for her kind. She has been a peacemaker, power broker, and heartthrob, too, among the chimps at Burgers Zoo in the Netherlands. When we meet her, she is sick, gaunt, fragile, and within weeks of dying. Curled up on the straw of her night quarters, she receives a visitor, an old friend, biology professor Jan van Hooff, nearing 80, who has known Mama for more than 40 years.

It takes a few moments for her to wake and to realize Jan is by her side, but when she does, she lights up, as de Waal describes it, in an “ecstatic grin,” expressing “immense joy.” Mama, perhaps sensing some trepidation from Jan, finds the strength to reach out to him — stroking his hair, embracing him, and patting the back of his head the way chimps “quiet a whimpering infant.” The moment, captured on video by a colleague’s cellphone was widely viewed.

De Waal knew Mama well — he’s written about her in earlier books. And it feels right that she launches this work. He uses his own research, some familiar from his other books, lots of it fresh, and weaves in thoughts from literature, art criticism, and a pile of work from others. “Since I don’t look at our own species as emotionally much different from other mammals, and in fact would be hard-pressed to pinpoint uniquely human emotions,” he writes, “we had better pay careful attention to the emotional background we share with our fellow travelers on this planet.”

As a student in the 1970s, de Waal realized that watching apes deepened his understanding of fellow humans. Now, he finds evidence in many species of behaviors that help inform thoughtful discussions of laughter, empathy, disgust, guilt, warfare, fairness, faithfulness.

Rats like to be tickled, and dogs sometimes limp when their owner does. Alex, a well-studied African gray parrot, seemed to know when he was being cheated out of a favored vegetable at the dinner table of psychologist Irene Pepperberg and would protest, yelling, “Green bean!” And sunglass-snatching long-tailed macaques at Balinese temples are known to extort treats from tourists by swapping items they just stole for more valuable ones, like a bag of crackers.

Prairie voles, unlike promiscuous meadow voles, maintain exclusive bonds with mates. Part of the magic is that the reward center of their brains is rich in receptors for oxytocin, a neuropeptide that fosters bonding not just in voles, but in all mammals, including us. Among these faithful voles, losing a mate causes such stress and depression that de Waal doesn’t hesitate to say that “these tiny rodents seem to know grief.”

This leads to one of the many insights about life that de Waal gained from his work with animals: “[T]he sad flip side of social bonding [is] loss.” Elsewhere, through Mama and the chimpanzees, he sees that “[p]ower and rank are different things.” Something as “simple” as smiling has complex variations and interpretations. Chimpanzees can show fear grins, after all, and we ourselves use smiles to appease, as seen in reprimanded children. As for empathy, there’s something called yawn contagion — experienced most by empathetic people — women more than men, by the way, and, it turns out, dogs are often triggered to follow suit when hearing their person yawn.

He also highlights examples of cruelty, such as an incident at Burgers Zoo in which a male chimpanzee is “butchered” by rivals. But an extended riff on the joy of laughter is a favorite of mine. De Waal fondly remembers such intense laughter at family meals that he “felt like dying,” having to leave the room in order to breathe. Laughing releases feel-good endorphins, and the “earliest laughter in our lives always occurs in a nurturing context as it does in other primates.’’ Gorilla mothers, for instance, begin tickling their babies to evoke laughter just days after birth.

Then de Waal reveals an observation valuable to understanding our social selves: “Humor is not central to laughter: social relationships are.” Ah, connectedness. “Anyone who wants to make the case that a tickled ape must be in a different state of mind from a tickled human child,” de Waal says, “has his work cut out for him.”

Laughter, he says, “reframes what we say or do.” His book too may help reframe how we see animals and our place among them. Ultimately, the conversational tone isn’t just a style, but a key to understanding — these are complex notions, he seems to say, but just use your common sense.

Hmm. We’re sharing tools with chimps.

MAMA’S LAST HUG:

Animal Emotions and What They Tell Us About Ourselves

By Frans de Waal

Norton, 326 pp., illustrated, $27.95

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Vicki Constantine Croke is the author of “Elephant Company: The Inspiring Story of an Unlikely Hero and the Animals Who Helped Him Save Lives in World War II.”