[jisaacstone]

The book "Mothers and Others" discusses this at length, positing not only did mothers have much more "Alloparental" support in the past, but this was the key fact that allowed the evolution of our big brains. That is, alloparental involvement was a necessary precursor to homo sapian big-brain evolution and the key thing that was lacking in other apes.

Very interesting and highly reccomended