On another brother

We had our 'big' ultrasound for Thing 3 on Wednesday.  It's a boy.  There were many tears shed by the girl that has wanted a sister for 5 long years.

Thursday morning, she walks in and throws herself down on my bed.

R: "Mommy, what happened to all of the girl sperm?"
M: "I have no idea, sweetie.  No idea."
R: "Why couldn't they get the directions right?  Why didn't they beat the boy sperm?  Are they lost somewhere inside your body?"  (The stream of related questions was seemingly endless.)
M: "I don't know, sweetie.  Nobody knows what makes some sperm get to the egg better than other sperm."

She keeps going with the questions until I advise her to take it up with her daddy.  Then she walked away, defeated and sighing.  Poor kid.  Too much knowledge of human reproduction can be a bad thing...