Learning to be funny

My just-about-four year old grandson, Michael, is learning to be funny, possibly a hereditary trait. Here is Michael telling us one of his first ever jokes:

Michael: "Why is six afraid of seven?"

Bobbi and Me: "Why?"

Michael: "Because eight.. no, wait. Let me start over."

Us: "OK."

Michael: (Thinks for a moment, then starts) "Why is six afraid of seven?"

Us: "Why?"

Michael: (Now confident) "Because seven eight nine!"

Bobbi: (Groans. She always groans at my jokes. So why not his?)

Michael: "No, it's funny. Really. It's really funny." (Pauses a beat) "See, it's because numbers don't have teeth. So they can't eat other numbers!"

So that's why it's funny!