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."
Spain provides paid maternity leave of 16 weeks with 30-50% of mothers returning to work (most full-time) after this, thus babies 4 months of age tend to be placed in daycare centers. Adult-infant ratios are about 1:7-8 first year and 1:16-18 second year. Public preschool education is provided for most children aged 3–5 years in "Infantil" schools which also provide primary school education.