It most certainly wasn't the time for it, but I laughed just the same. I'd been asked the same thing when I had my little 'I am female' tantrum in Doc's hospital.

"It's relatively simple, all things considered," I replied at last, looking at the baby in Helen's arms. "There are very few of us with the potential to become mothers. One for every thousand, or something like that. Once the decision is made, the mother divides herself. Every cell becomes a new life and carries with it the mother's memories, so information isn't lost between generations."