The study of human evolution is by now about much more than bones and stones. In 1965 a remarkable book—Irven DeVore’s collection Primate Behavior (which led me to study with DeVore)—made what then seemed a radical claim: We will never understand our origins without intensive study of the wild world of our nonhuman relatives. A handful of scientists, including Jane Goodall, set up tents in distant jungles and savannas. Following monkeys, apes, and other creatures in their habitats, these scientists turned their notes and observations into voluminous, quantitative data. DeVore and others devoted themselves just as rigorously to the remaining human hunter-gatherers, found on every habitable continent except Europe—our biological twins, living under conditions resembling the ones we evolved in.

The multifaceted effort was new and ambitious, but the idea was old. DeVore had hanging in his office an 1838 quote from Darwin’s notebook: “Origin of man now proved … He who understands baboon would do more towards metaphysics than Locke.” It’s an aphorism that calls to mind one of my favorite characterizations of anthropology—philosophizing with data—and serves as a perfect introduction to the latest work of Richard Wrangham, who has come up with some of the boldest and best new ideas about human evolution.

In his third book, The Goodness Paradox: The Strange Relationship Between Virtue and Violence in Human Evolution, he deploys fascinating facts of natural history and genetics as he enters a debate staked out centuries ago by Thomas Hobbes and Jean-Jacques Rousseau (among other philosophers), and still very much alive today: how to understand the conjunction of fierce aggression and cooperative behavior in humans. Why are we so much less violent day-to-day within our communities (in pretty much all cultures) than our closest primate relatives, chimpanzees, are within theirs? At the same time, how is it that human violence directed toward perceived enemy groups has been so destructive?

Wrangham, who teaches biological anthropology at Harvard, was mentored by both Goodall and DeVore. He was in a sense working toward this latest venture in his two previous books, which explore the opposing poles of behavior. Renowned for his meticulous fieldwork, especially with chimps in Uganda’s Kibale National Park, Wrangham showed just how common chimp brutality is. Goodall had acknowledged with frank regret that her beloved chimpanzees could be quite violent. One mother and daughter killed the infants of other females in their group. Males often coerced and beat females, and would sometimes gang up and attack a chimp from another group.

At Kibale, large groups of chimps range together, and aggression escalates accordingly. Wrangham observed as these bigger parties of males got excited and went out on “patrol” in what looked like an organized way: They walked along their territorial border, attacking lone chimps from neighboring communities when they came across them en route. In his 1996 book, Demonic Males, co-authored with Dale Peterson, Wrangham recapped this and other evidence to draw a dire portrait of humanity (the male version) as inherently violent by evolutionary legacy. Here was vivid support for a Hobbesian view of human nature, rooted in genetics.