According to Chris Knight, the first humans were few; then the population "exploded .... Population expansion on such a scale is inconsistent with female tolerance of infanticide, harassment, or the heavy costs to mothers of male philandering and double standards. If unusually large numbers of unusually large-brained offspring were being successfully raised to maturity, the quality of childcare must have been exceptional. We know what the optimal solution would have been. There can be no doubt that mothers would have done best by ... taking advantage of every available childcare resource."
The service is known as day care or childcare in the United Kingdom, North America, and Australia and as crèche in Ireland and New Zealand. According to Oxford Living Dictionaries, child care in two words can in addition have the broader meaning of the care of a child by anyone, including the parents, but US dictionaries do not record that spelling or meaning. In English-speaking and other conservative countries, the vast majority of childcare is still performed by the parents, in-house nannies or through informal arrangements with relatives, neighbors or friends, but most children are in daycare centers for most of the day in Nordic Countries, for example. Child care in the child's own home is traditionally provided by a nanny or au pair, or by extended family members including grandparents, aunts and uncles. Child care is provided in nurseries or crèches or by a nanny or family child care provider caring for children in their own homes. It can also take on a more formal structure, with education, child development, discipline and even preschool education falling into the fold of services.