How was I born?

A boy was assigned a paper on childbirth and asked his parents, "How was I born?"

"Well honey..." said the slightly prudish parent, "the stork brought you to us."

"Oh," said the boy. "Well, how did you and daddy get born?" he asked.

"Oh, the stork brought us too."

"Well how were grandpa and grandma born?" he persisted.

"Well darling, the stork brought them too!" said the parent, by now starting to squirm a little in the Lazy Boy recliner.

Several days later, the boy handed in his paper to the teacher who read with confusion the opening sentence: "This report has been very difficult to write because there hasn't been a natural childbirth in my family for three generations."