Melody Dye passes along some research suggesting that our slow cognitive development is key to our intelligence as a species:
In a recent article in Current Directions in Psychological Science, Sharon Thompson-Schill, Michael Ramscar and Evangelia Chrysikou make the case that this very helplessness is what allows human babies to advance far beyond other animals. They propose that our delayed cortical development is precisely what enables us to acquire the cultural building blocks, such as language, that make up the foundations of human achievement. Indeed, the trio makes clear that our early vulnerability is an evolutionary “engineering trade-off,” much like the human larynxwhich, while it facilitates the intricate productions of human speech, is actually quite a precarious adaptation for anyone trying to swallow safely. In the same way, they suggest, our ability to learn language comes at the price of an extended period of cognitive immaturity.
Jonah Lehrer adds his two cents.