Fascinating theory. The hard work of raising helpless babies is part of the natural selection process that made us as a species so intelligent.
Natural selection favors humans with large brains, because those humans tend to be smarter. This may create evolutionary incentives for babies that are born at an even earlier developmental stage, which require more intelligence to raise. This creates the dynamic: over time, helpless babies make parents more intelligent, which makes babies more helpless, which makes their parents more intelligent, and so on. —The New Yorker