Sexual combat is not a monopoly of the human species. As Sarah Blaffer Hrdy argues in this spellbinding book, war between male and female animals has deep roots in evolutionary history. Her account of family life among hanuman langurs--the black-faced, gray monkeys inhabiting much of the Indian subcontinent--is written with force, wit, and, at times, sorrow. Male hanumans, in pursuit of genetic success, routinely kill babies sired by their competitors...