NEAR THE END of The Origin of the Species, Charles Darwin boldly predicts: “Much light will be thrown on the origin of Man and his history.” That prediction was prescient but premature. Half-baked extrapolations of his theories were almost immediately used to shore up pernicious imperial enterprises, to buttress Marx’s tendentious view of history, and to justify racism and anti-Semitism. In short, The Origin initially fostered a dark age of misappropriations, rather than enlightenment.

None of these abuses were Darwin’s fault, any more than the Thirty Years War was the fault of Copernicus. Indeed, Darwin’s actual writings on human origins — The Expression of the Emotions in Man and Animals and The Descent of Man ­— were characteristically meticulous applications of his scientific models. And, in addition, he was far more concerned with assembling evidence for our origins as a unified species and for our consequent universal characteristics than he was with differences among groups of humans, let alone human competition among groups or races or classes or nations.

The fact that ‘Darwinism’ (the supposedly deterministic struggle for existence) was used to justify many of the nineteenth and twentieth centuries’ atrocities created a chilling effect: by the late twentieth century, the social sciences were extremely leery of fraternizing with anything smacking of so-called Darwinism. Even so, new applications of evolutionary science were emerging in ever more compelling ways. By the end of the millennium, it was next-to-impossible to avoid conversations that linked biology to human behavior.

Two years after the bicentennial of Darwin’s birth and the sesquicentennial of The Origin of Species, a steady stream of new books marks his influence in twenty-first century scholarship. As several of them demonstrate, Darwin’s new descendants have returned to the ancestral method. Based on carefully developed models and tested with real evidence, they demonstrate that the work of applying Darwin to the social sciences is just getting started. Evolution is ever more thoroughly ensconced in the realm of what science historian Thomas Kuhn famously called “normal science,” tackling new individual problems but within a familiar paradigm, instead of throwing out the paradigm and building a new one. Darwin’s theory is being applied as a matter of course not just to biology but to psychology, anthropology, sociology, economics, linguistics, political science, even history. This is not to say that it is cannibalizing those fields. Nor is it taking the place of these fields’ standard theories and methods. Rather, it expands and informs them by taking into account our growing knowledge of human beings as animals who, to borrow the last words of The Origin, “have been, and are being, evolved.”

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Charles Nunn is an evolutionary anthropologist, but his new book ranges beyond that field. More than a technical handbook, it is also a marvelous summary of recent research on everything from how the “intermembral index” (arm length divided by leg length) has evolved among primates to how testicle size relates to mating systems — it tracks body size up to a point, but in those species where females mate with lots of males, the latters’ best course has been to evolve outsize go...