When does zero begin?

Rowan: "Dad, when does zero begin?

Me: "What do you mean?"

Rowan: "Like... when does zero begin?"

Me: "You need to use other words."

Rowan: "Um, when does zero begin when a baby is born?"

Me: "Aha. OK, great question. When do you think?"

Rowan: "When they come out of Momma."

Me: "OK, what are they before they come out?"

Rowan: "Well, maybe zero is when they're inside and they're this big." (Holds hands out measuring the size of a large bass.)

Me: "OK, what are they before that?"

Rowan: "Well, maybe it's when they're thisss tiny." (Presses tips of fingers together as if holding a speck of dust."

Me: "OK, what are they before that?"

Rowan: "Dad, have you ever been in jail?"