Are you human?

From a book I’m currently reading:

“We were all terrible when we were little. Did you ever see how vicious and monstrous kids are to each other? And I’m not just talking about in the sandbox either, where they bang each other over the head with their trucks! Teenagers…God, teach them for a while if you want to learn about mean. There is nothing in the world as small and malicious and self-centered as a fifteen-year-old. No, Joey, don’t crucify yourself over it. People don’t become human until they’re around twenty-two years old, and then they’re just beginning.”