"All You Zombies"

"All You Zombies" was a short story written by Robert A. Heinlein. It is one of the most well known science fiction short stories and it was written in one day over 50 years ago. This story involves time travel and several time paradoxes. The story is about a young women who gets pregnant by an older man but during childbirth, the doctors realize their young women has both male and female reproductive organs. Complications of giving birth force the young women to have a sex change. Now, his baby is taken away and he goes on with his life but goes back in time, with someone named the Bartender, later on and impregnates a young women. The Bartender is the one who goes forward in time an takes the baby and puts it in an orphanage in past. It turns out every character in this story is the same person. At the end the Bartendder is contemplating his life and says "I know where I came from—but where did all you zombies come from?".