Richard Wrangham, a primatologist and anthropologist, a specialist in the evolution of primates, professor at Harvard University, clearly and thoroughly breaks down a scientific debate on the most important questions: why, for humans—members of a single biological species—both astonishing kindness and unimaginable cruelty are characteristic; how these qualities, sometimes going far beyond common sense, appeared and became established during the evolutionary history of humankind; where our moral feelings come from, our notions of good and evil; and, most importantly, whether our evolutionary paradox condemns us to a perpetual threat of violence.