Human life histories differ from those of other closely related species in ways that significantly affect parental care and childhood. Most explanations for the hominization of life histories incorporate ideas about social interdependence and cooperative breeding. While cooperation for the purposes of raising children is often presumed to be ancient, it leaves no known fossil record or genetic signature. To address this empirical gap, I will first discuss the evolution of parenting and childhood, and then develop a simulation that looks at the question, when do mothers need others? I will conclude by asking what is it that we can actually say about the past, and suggest from model results that an age division of labor and exchanges between mothers and juveniles are an important gateway in the evolution of human sociality and cooperation.