What happens to a monkey who grows up without a mother? Had a biologist been asked decades ago, he or she probably would have answered that if the animal were kept clean, well-nourished, and disease-free it would develop relatively normally. Indeed, until the second half of the twentieth century it was widely believed that the role of the mammalian mother was primarily to provide her children with food (milk especially), warmth, and protection. That she might also play an essential role in her offsprings’ behavioural development would have been a rather unusual thought.