After their baby was born, the panicked Barry went to see the Obstetrician.
"Doctor," Barry said, "I don't mind telling you, but I'm a little upset because my daughter has red hair. She
can't possibly be mine."
"Nonsense," the doctor said. "Even though you and your wife both have black hair, one of your ancestors may have
contributed red hair to the gene pool."
"It isn't possible,"Barry insisted. "This can't be, our families on both sides had jet-black hair for
generations."
"Well," said the doctor, "let me ask you this. How often do you have sex?"
Barry seemed a bit ashamed.
"I've been working very hard for the past year. We only made love once or twice every few months."
"Well, there you have it!" The doctor said confidently