It has long seemed self-evident that women care for babies and men do other things. Hasnt it always been so? When evolutionary science came along, it rubber-stamped this venerable division of labor: mammalian males evolved to compete for status and mates, while females were purpose-built to gestate, suckle, and otherwise nurture the victors offspring. But come the twenty-first century, increasing numbers of men are tending babies, sometimes right from birth. How can this be happening? Puzzled and dazzled by the tender expertise of new fathers around the world – several in her own family – celebrated evolutionary anthropologist and primatologist Sarah Blaffer Hrdy set out to trace the deep history of male nurturing and explain a surprising departure from everything she had assumed to be normal.