He noticed a blond hair growing on his finger this morning. At lunch he had told me of his experiences wiping his bottom after a profound bout of diarrhea. With the aid of a mirror, he showed me how his tiny hole could stretch to let out big poops. I told him vaginas were stretchy in a similar way. I told him if boys could give birth, maybe the babies would come out of the hole in the penis.
A few minutes later, Charlie said, "I know why you have hair. Because when the baby comes out and is cold, your hair can keep the baby warm."
Like a little fur coat? I suggested. He nodded.