"Mama," my nine-year-old son said. "Did you know we're closely related to amphibians?"
I looked at that boy funny. "What do you mean, Bubba? Amphibians are cold-blooded animals, and humans are warm-blooded."
"Humans and frogs can both hang out in water and on land."
"But what about the warm-blooded, cold-blooded thing?" I asked.
He thought about that a second. "Well, frogs are cold-blooded and they croak. When humans become cold-blooded, they croak."