There are only a few names within the field of primatology that are recognizable to the general public, and Frans de Waal certainly falls into this category. The noted Emory University primatologist has studied our closest living relatives, chimpanzees and bonobos, for nearly 30 years. He has authored countless scientific articles and texts, as well as several books. While his previous works have focused on such topics as chimpanzee politics and ape social complexity, de Waal's 2005 book looks at similarities between humans and our two closest living ape relatives. Entitled Our Inner Ape: A Leading Primatologist Explains Why We Are Who We Are, this book looks at various aspects of what most people believe to be distinctively human characteristics, including love, kindness, and power, explaining them in the context of our evolutionary cousins: chimpanzees and bonobos.
Yet instead of simply describing cultural traits that we may share with chimpanzees or bonobos, de Waal continually poses the question: to which species we are more similar, the often-violent chimpanzee, or the peaceful and overtly sexual bonobo? De Waal attempts to find an answer to this question through the examination of the human characteristics of power, sex, violence, and kindness.
One of the strengths of de Waal's writing is his vast amount of first-hand experience, having worked with chimps and bonobos at facilities both in his native Netherlands and in the US. De Waal uses these experiences to help to explain important similarities between human and chimpanzee/bonobo cultures. In chapters on power, sex, violence, and kindness, he offers powerful examples of how chimpanzees or bonobos exhibit the characteristic in question, often in a very humanlike manner. Indeed, it is these examples, peppered throughout each chapter, that allow this book to be enjoyed by a wide audience.
For instance, in the chapter on power, de Waal describes a struggle for male dominance that took place between three chimpanzees in the Arnhem zoo in Amsterdam. In this touching story, de Waal tells how the alpha male, Luit, was attacked by two other chimps, Yeoren and Nikkie, as a response to Luit's fast ascent to power within the group. Yeoren and Nikkie had formed an alliance, whose purpose was to get rid of Luit and then take over control of the group. Unfortunately, Luit did not survive the encounter, and this display of both violence and strategy leads de Waal to remark, "Those two had been plotting against him in order to take back the power they had lost. The shocking way they did so opened my eyes to how deadly seriously chimpanzees take their politics" (p 43). Noting that political murder is also present in our species, de Waal observes that the struggle for power among both chimpanzees and humans illustrates just how closely related to each other we are.
However, though humans' violent nature can be compared accurately to that of chimpanzees, perhaps our sex drive can be compared more accurately to that of bonobos. Bonobos used to be known as "pygmy chimpanzees," but have since been upgraded to their own separate species within the family of great apes. Though they are physically similar to chimpanzees, their social structure and culture is markedly different, especially with regard to sex. De Waal examines human sexuality in the same way he examines human violence: in the context of our ape relatives. Indeed, de Waal begins his discussion on sexuality by asking, "Why are people and bonobos such sexual hedonists? Why are we endowed with sexual appetites beyond those needed to fertilize the occasional egg and beyond the partners who make this possible?" (p 96). De Waal then continues on an exploration of multiple aspects of both human and ape sexuality, covering such topics as homosexuality, child-rearing, and infanticide. He then ends his discussion on how we came to differ from bonobos in our sexuality, pointing to the evolution of the nuclear family as a step towards reduction of overt sexual competition, which in turn increased cooperation among these family units. De Waal finally proposes that our success as a species may have been a result of an abandonment of the "bonobo lifestyle" in favor of a tighter control of our sexual expressions.
De Waal's final chapter takes the characteristics on which he focuses — power, sex, violence, and kindness — and asks which species humans are more similar to: chimpanzees or bonobos? However, de Waal argues that attempting to categorize ourselves in this way is fruitless, as we humans are much too bipolar: we cooperate and we compete,we are characterized by hate and by love. Further, de Waal argues that if we are "essentially apes, or at least descended from apes,we are born with a gamut of tendencies from the basest to the noblest. ... our morality is a product of the same selection process that shaped our competitive and aggressive side"(p 237). In other words, when attempting to discover from where our humanity evolved, we must look towards both our closest living relatives: chimpanzees and bonobos; and that both these species represent our two "inner apes."
De Waal's exploration of our "inner ape" is largely readable and often engaging, and even a reader with only a general interest in primatology would have no trouble understanding the arguments that de Waal presents. However, advanced primatologists and students might find the subject matter rather basic, as there is not much new research discussed in the book. In addition, the reliance on vivid, often emotional examples may put off some veteran primatologists who would prefer a more straightforward or dry approach. Yet it is clear that de Waal was not trying to create a data-heavy textbook on human and ape cultures. Rather, de Waal's argument that humans exhibit important qualities of both chimpanzees and bonobos is well-developed, organized, and is complemented by excellent examples from his years in close contact with these animals. As a result, the reader is left with a solid understanding of what it means to be human, as well as what it means to be an ape; something that would be appealing to anyone with a general interest in anthropology and psychology.