You look like a monkey, and you act like one, too

"Our Inner Ape: A Leading Primatologist Explains Why We Are Who We Are"
by Frans de Waal
Riverhead, 274 pp., $24.95

Even staunch supporters of Darwinian evolution acknowledge the reason that many people find that theory hard to accept. We humans see ourselves as rational beings with manners and ethics, while apes are fundamentally different creatures that behave like — well — animals.

Emory University primatologist Frans de Waal would not agree. If we really want to understand what makes us human, de Waal argues in "Our Inner Ape," we should not focus on our differences with apes, but rather examine the "fascinating and frightening parallels between primate behavior and our own, with equal regard for the good, the bad, and the ugly." That is precisely what he does in the book, with a wealth of stories and an entertaining style that does not sacrifice scientific depth or objectivity.

He focuses on chimpanzees and bonobos because they are closest to humans, sharing a common ancestor as recently as 5.5 million years ago.

The bonobo has been known less than 80 years. At first, it was called a pygmy chimpanzee but, as de Waal notes, the two species are as physically different "as a Concorde is from a Boeing 747."

"Even chimps would have to admit that the bonobo has more style," he asserts. "A bonobo's body is graceful and elegant ... Females have breasts; they are not as prominent as in our species, but definitely A-cup compared to the flat-chested other apes."

"Chimps," he continues, "... look as if they work out every day. Bonobos have a more intellectual appearance ... [with] an eerily humanlike posture" comparable to "Lucy," modern humans' famous Australopithecus ancestor.

Appearance aside, the most remarkable differences between the two species are behavioral. Chimpanzees live in Machiavellian hierarchical male-centered social groupings, writes de Waal. Chimpanzee dominance and alliances depend on confrontation and physical prowess.

Bonobos, on the other hand, "make love, not war." They live in female-centered groups where erotic touching between individuals regardless of gender or age serves as a social lubricant.

Sex is remarkably casual, and "they know all the positions of the Kama Sutra, and even some positions that are beyond our imagination (such as both partners hanging upside down by their feet)."

Where do humans fit into this spectrum of behaviors? That question is always open for discussion as de Waal shares lively stories from his 30 years of primatology research in a series of long and well-crafted chapters about the lineage of ape species, dominance, sexual politics, violence and reconciliation, and kindness and altruism.

In a shorter concluding chapter, de Waal gives Darwin's theory of natural selection an almost Marxist dialectical twist. Human nature is the result of "tamed contradictions," he writes.

"Being both more systematically brutal than chimps and more empathic than bonobos, we are by far the most bipolar ape. Our societies are never completely peaceful, never completely competitive, never ruled by sheer selfishness, and never perfectly moral." He ends by speculating about our species' future evolution.

Some readers will find that chapter intriguing, but others will find it discordant. For most of its pages, "Our Inner Ape" presents the evolutionary heritage of human nature, or as the subtitle states, "Why we are who we are."

But when it turns to the open question of who — or what — our species may become, even the most committed Darwinist may seek a new theoretical or philosophical foundation.

Fred Bortz is a children's book author (www.fredbortz.com) and science book critic (www.scienceshelf.com).