A genuine field office, the Yerkes space is sparse and wood-paneled, with furnishings that could kindly be described as “retro”—a scarred desk, a grimy phone that looks to date to about 1965, an electric fan. A lab coat and a large pair of binoculars hang on the wall.

It’s the wide Plexiglass window at the far end of this office that makes it de Waal’s favorite. The windshield-like opening directly overlooks a chimpanzee habitat, where a multigenerational colony of fifteen chimps lounges in the wan winter sun. Draped over tire swings and playground equipment, the chimps appear relaxed and content—until they catch sight of research specialist Devyn Carter approaching with a bucket of bananas. Immediately the atmosphere is charged with energy as the chimps begin to jump up, scream, and emit the “panthoots” that signal excitement in anticipation of special food.

De Waal, Emory’s Charles Howard Candler Professor of Psychology and director of Yerkes’ Living Links Center, also receives a friendly greeting from these chimpanzees; he has spent more than two decades studying our closest primate cousins at Yerkes and ape communities around the world. Untold hours of scrutinizing the social behaviors of apes have yielded five successful books, including The Ape and the Sushi Master , Chimpanzee Politics , and Los Angeles Times Book Award winner Peacemaking Among Primates . His depth of expertise secures him a top spot among the most noted primatologists in the world.

But de Waal has never applied his formidable knowledge of apes to the task of analyzing human behavior—until now. In his latest book, Our Inner Ape , he turns his powerful binoculars on his own species, using ape society as the context for examining some of the most fundamental, complex, and intense manifestations of human nature.

The core ideas of Our Inner Ape are brought to life by both engaging anecdotes about ape society—usually observed by de Waal himself and described in an easy, conversational tone—and common-sense, lively references to human culture. “There is the sort of popularization I do in the book, the anecdotal evidence, but the other side is the viable research,” he says. “I think when people read the book, they may not have that impression.”

With its casual, accessible style and keen insights about human as well as primate behavior, de Waal’s sixth book has received top reviews and already has appeared in twelve languages; a fifteen-city book tour brought him to crowded lecture halls around the world, and he has made dozens of radio and TV appearances, including three on National Public Radio.

Our Inner Ape was named a New York Times Notable Book of the Year and a Seed Magazine Top Ten Science Book for 2005. It received a coveted “starred review” in Publishers Weekly , which wrote: “de Waal offers vivid, often delightful stories of politics, sex, violence, and kindness in the ape communities he has studied to illustrate such questions as why we are irreverent toward the powerful and whether men or women are better at conflict resolution. Readers might be surprised at how much these apes and their stories resonate with their own lives and may well be left with an urge to spend a few hours watching primates themselves at the local zoo.”

While a number of comparative studies of apes and humans have relied heavily on the chimpanzee, Our Inner Ape gives equal weight to the lesser-known bonobo, a slightly smaller, more refined primate who relies less on aggression and more on eroticism to solve problems. By including both these hairy relatives—our genetic twins but for 1.5 percent difference in DNA—de Waal illuminates the wide range of primate behaviors that have arguably shaped our own branch of the evolutionary family tree.

One of his intentions for the book, de Waal says, was to offer an alternative view to the dominant idea developed in the 1960s and 1970s, supported by the startling field observations of researchers such as Jane Goodall, that apes and humans share an innate tendency toward aggression and violence, disguised in people only by a “veneer” of practiced civility—the “killer ape” theory. De Waal is perhaps more closely aligned with Desmond Morris, author of the 1967 The Naked Ape —possibly the most popular book ever written comparing apes and humans—in his approach: to acknowledge the wide range of ape behavior, from aggression to tenderness, shocking violence to equally surprising compassion, and objectively try to identify what these similarities and differences might mean to human society.

“For many years, it was an established notion in the field that we became what we are because we are descended from aggressive animals,” de Waal says. “My position is somewhat different. After World War II, it was logical to think about aggression. But at some point, we have to acknowledge other aspects of human nature such as empathy, cooperation, reciprocity. We are a highly cooperative species at the same time that we are highly aggressive.”

In his review for the scientific journal Nature , Robert Sapolsky of the Department of Biological Sciences at Stanford University wrote, “In this excellent book for the public, Frans de Waal tackles some exasperating misconceptions about the evolution of the social behavior of apes, particularly humans. ... This is a rarity, a superb scientist producing an excellent book for non-specialists. This should be required reading for the opinionated cousins (or better yet, world leaders) whose ancient encounters with [anthropologist] Robert Ardrey or [zoologist] Konrad Lorenz have led them to believe that they understand what kind of ape we are.”

While the intensely political, often aggressive chimpanzee supports the killer ape theory to some degree, the peaceable, sex-loving, female-dominated bonobo—whom de Waal refers to as the “hippies of the primate world”—exposes a different side of primate life. Long thought to be merely a smaller version of the chimpanzee, bonobos were only recognized in 1929 as a separate species. Sapolsky calls bonobos the “antidote” to the “human-as-killer-ape destiny.”

“We are blessed with two close primate relatives to study, and they are as different as night and day,” writes de Waal in Our Inner Ape . “One is a gruff-looking, ambitious character with anger-management issues. The other is an egalitarian proponent of a free-spirited lifestyle. . . . The power-hungry and brutal chimp contrasts with the peace-loving and erotic bonobo—a kind of Dr. Jekyll and Mr. Hyde. Our own nature is an uneasy marriage of the two.”

Going hand-in-hand with theories of inherent aggression is the concept that we are bred to be “selfish” in order to perpetuate our species and dominate others, a popular 1980s-era justification for hedonism and capitalist greed. But de Waal argues that surviving Darwinian-style does not make us “selfish,” any more than a snowball rolling down a hill demonstrates selfishness by growing bigger; nor does such a notion account for the range of altruistic social behaviors exhibited by both humans and apes.

When a bird flew into the glass enclosure of a bonobo named Kuni, de Waal recounts, she picked it up and tried to help it fly away again. Rather than comforting the starling like a fellow ape, Kuni carried it to the top of a tree, carefully spread its wings, and launched it gently into the air, showing that she recognized its needs as distinct from her own—a remarkable act of empathy. Humans show the same inclination when they help strangers without regard to their own reward, such as stopping to assist accident victims or giving away money to people they have never met.

“I think our motivations often transcend the reason why a behavior evolved,” de Waal says. “Acts of helping may have originally evolved in context for their survival value, but are now applied to situations outside that.”

In his previous books Chimpanzee Politics and Bonobo: The F orgotten Ape , de Waal explored the cunning Machiavellian tendencies of male chimps and the more egalitarian, Rousseauian tendencies of bonobos. Our Inner Ape uses the chimp-bonobo-human triad to examine four core aspects of both animal and human social interaction and expression: power, sex, violence, and kindness.

Chimpanzee society, de Waal writes, is dominated by male politics, the constant, complicated shifting of power and strategic alliances. Not unlike the human contestants on the hit reality TV show Survivor , chimps’ rank and success depends on their ability to align with and influence other males. This competitive climate frequently erupts into violence, which in some cases can be fatal. In what de Waal describes as the saddest moment of his career, a favorite chimpanzee leader, Luit, was savagely set upon by two rivals who had teamed up and later died of his injuries. The restless hierarchy of chimpanzee groups, de Waal writes, may reflect our natural tendency toward a system of checks and balances.

“Democracy,” he writes, “is an active process: it takes effort to reduce inequality. That the more dominance-oriented, more aggressive of our closest relatives best illustrates the tendencies on which democracy ultimately rests is not surprising if we look at democracy as born from violence, as it most certainly is in human history. ... It has never been handed to us for free; it has always been wrested from the powerful.”

By contrast, in a section entitled “Girl Power” de Waal describes how females run the show in bonobo communities, controlling the food supply and wielding considerable authority over relationships and mating. Even the male bonobo hierarchy, de Waal says, is actually determined by the influence of the mothers.

Although human society, at least in most cultures, could never be said to be female-dominated, de Waal finds similarities in the way female bonobos relate to one another. “In both apes and humans,” he writes, “the female hierarchy is less contested and consequently requires less enforcement.”

In stark contrast to chimpanzees, bonobos frequently use sex rather than physical aggression to resolve conflicts and play out politics. With their large, overt genitals, bonobos are easily among nature’s most erotic animals, initiating sex on average every hour and a half as compared to chimps’ relatively prudish habit of every seven hours.

“The most significant point about bonobo sex is how utterly casual it is, and how well integrated with social life,” de Waal writes. “We use our hands in greetings, such as handshakes and pats on the shoulder, whereas bonobos offer genital handshakes.”

They also are universally bisexual, with same-sex pairs engaging in sexual activity as often and as casually as opposite-sex pairs; indeed, females rubbing their genitals together with obvious sexual pleasure is the “political cement” of bonobo society, de Waal says. Sex is used to bond, to make up, to show affection, to barter for food, to show respect or submission, and even occasionally for the old-fashioned purpose: to make baby bonobos. But while maternity is central to bonobo groups, male bonobos generally have no idea which offspring are theirs, since they are likely to have had sex with multiple females—as have all the other males. One theory is that this prevents males from killing infants who may someday pose a threat to their authority—the leading cause of infant deaths among chimps.

With its constant, casual sex, bonobo life may look like a lot of fun—and humans do emulate aspects of it, such as having sex for pleasure rather than strictly reproduction. But ultimately it also illustrates why that approach won’t work for humans, de Waal says. Our ancestors were the inventors of the nuclear family: infants’ survival depended on their fathers’ commitment to protecting them, so we evolved to favor couples with children. Even if we haven’t quite perfected this model, it’s universally acknowledged as the ideal.

“It’s no accident,” de Waal writes, “that people everywhere fall in love, are sexually jealous, know shame, seek privacy, look for father figures in addition to mother figures, and value stable partnerships. The intimate male-female relationship implied in all of this, which zoologists have dubbed a ’pair-bond,’ is bred into our bones. I believe this is what sets us apart from the apes more than anything else.”

What de Waal hopes readers take from Our Inner Ape is a sense that our evolutionary makeup leaves room for a much wider range of motivation and behavior than scientists may previously have thought.

“We have an enormous spectrum of behavior, so don’t believe claims that we are inherently nasty, aggressive, selfish, and uncooperative. My argument is that we have the potential to be everything we want to be,” he says. “Our job is to bring out what we want. Certainly, I would argue that under certain circumstances, we will be aggressive. If you want to reduce human aggression, you must limit the situations in which it arises.”

Like our primate cousins, he says, we are able to feel empathy, which can lead us to act with both great kindness and terrible cruelty—behavior born of the ability to imagine what others feel.

But the brighter message is that the “killer ape” is only one side of the story; on the other is the bonobo Kuni, gently spreading the wings of a bird to try to help it fly. As de Waal points out, when people try to insult one another by claiming they are “acting like animals,” they should think twice about whether that’s really such a bad thing.