I remember reading an old story by Robert Heinlein, in which a human being had literally created himself. Don't knock the biological impossiblity, only the theoretical. In short, this is the plot:
A girl is born in 1945, and grows into a young woman. She starts working for an old bartender and meets an older man in the bar in 1963, falls in love with him, gets pregnant but the man disappears leaving her alone. Nine months later, during labor, it is discovered that she is intersexed and an operation must be performed to save her life: a sex change. Nonetheless the baby, a girl, is born and given up for adoption...to the bartender. As years go by, "he" who was once "she" joins a time-traveling program and goes back to this bar in 1963, sleeps with an 18 year old girl, and then leaves her, then goes back to his own time. Many more years go by, and the now older man decides to go back in time and start a bar. When one of his employess gives birth out of wedlock, he decides to adopt the infant girl. He then goes back even further in time to 1945, where he raises the child as his own...that child being himself.
So yes, this person is his own mother, father, and grandfather(?), and whatever else you can figure out...so how did he/she come into being in the first place?
