I have read a few articles by Alison Gopnick, a delightful writer on subjects of psychology and philosophy. Here she discusses the impact of our disrupted lives and its effect on the child-grandparent bond.
To exercise these impressive early learning abilities, you need elders who can protect and nurture you. Curious children depend on caring adults. So, the other part of the life-history change was the evolution of more caregiving, especially including the caregiving that elders can provide.