What's a Girl? Vertebrate or Invertebrate?

The other night at dinner, Ben posed the question: "What's a girl?"

Mindy and I looked at one another trying to decide how to answer such a broad question. Then Ben let us off the hook. He has been learning about classifications of animals at school recently and so the question was more specific.

"Is a girl a vertebrate or an invertebrate?"

Whew, we can answer that one.

"A girl is a vertebrate," I say with relief.

But then he follows up with this gem. "So are boys invertebrates?"

Naturally, I'm left to answer this one as Mindy is occupied with trying not to dissolve into gales of laughter.

So I explain that all humans are vertebrates and both boys and girls are humans. Then I start to quiz him on what animals he is learning about in school. He starts with some "I don't know"s but then clearly doesn't want to talk about it anymore because he says in his best commanding tone, "Less talking, more eating."

I guess he told me.