Really, it's just the plain old facts of life. A hen ovulates without a rooster just like a woman ovulates without a man. I always wonder why people would ever believe that a hen wont lay without a rooster--doesn't make any sense at all.
Here one for you... My son came home and said his friends don't believe him that a rooster is a chicken! He went back after checking with me and told them they were wrong! One boy checked with a teacher who disagreed with my son!
Oh! This drives me nuts! I've used both replies of "well, don't you still ovulate if you don't have a boyfriend?" and "do you think the chickens at the egg factories have roos stuffed in those little cages with them?"