Being childlike is what makes us able to live in a society. We explore new things, don't stop learning, and forgive mistakes made along the way. Like wolves, who started being more like how they are in their puppy phase (playful, friendly, exploratory), thereby being possible to domesticate and now called dogs, we've domesticated ourselves (from the common ancestor we had with great apes) in that there was apparently an evolutionary advantage to be less physically imposing and more like, well, as we are today
(Based on what I remember from a books called Tamed by Alice Roberts)