According to the Greek creation myth, we are so much spilt milk; a splatter of the goddess Hera's breast milk became our galaxy, the Milky Way. But while mother's milk may be the essence of nourishment, it is the milk of other mammals that humans have cultivated ever since the domestication of animals more than 10,000 years ago, originally as a source of cheese, yogurt, kefir, and all manner of edible innovations that rendered lactose digestible,...