We also assume that "mother" and "father" are exclusive terms, though in other cultures, these terms are applied to a variety of aunts, uncles and other adults. Kinship is not exclusively biological, after all, and you need a brood to raise a brood. Cooperative child-rearing is obviously convenient, but some anthropologists believe that it also serves another more important function: Multiple caregivers enhance the cognitive skills of babies and young children. Any family in which there are parents, grandparents, nannies and other concerned adults understands how readily children adapt to different caregivers. Surely this prepares them better for life than stressed-out biological parents alone.
Baby as accessory: Gisele Bündchen with baby Benjamin (Getty Images)