If you have a strategy of having these very finely shaped innate modules just designed for a particular evolutionary niche, it makes sense to have those in place from the time you're born. But you might have a more powerful strategy. You might not be very well-designed for any particular niche, but instead be able to learn about all the different environments in which you can find yourself, including being able to imagine new environments and create them. That's the human strategy.
But that strategy has one big disadvantage, which is that while you're doing all that learning, you are going to be helpless. You're better off being able to consider, for example, should I attack this mastodon with this kind of tool or that kind of tool? But you don't want to be sitting and considering those possibilities when the mastodon is coming at you.
The way that evolution seems to have solved that problem is to have this kind of cognitive division of labor, so the babies and kids are really the R&D department of the human species. They're the ones that get to do the blue-sky learning, imagining thinking. And the adults are production and marketing. We can not only function effectively but we can continue to function in all these amazing new environments, totally unlike the environment in which we evolved. And we can do so just because we have this protected period when we're children and babies in which we can do all of the learning and imagining. There's really a kind of metamorphosis. It's like the difference between a caterpillar and a butterfly except it's more like the babies are the butterflies that get to flitter around and explore, and we're the caterpillars who are just humping along on our narrow adult path.
Link. Watch the video, too.