In the Garden of Eden, over 6000 years ago, God says to Adam, "Adam I have a surprise for you. She's called a woman."
"What's a woman?" asks Adam.
"Well, you're going to find out," replies God. I want you to go down into the valley— "
"What's a valley?" asks Adam. Adam hasn't learned many words yet, so God patiently explains.
"And then cross the river— "
"What's a river?" Again God explains.
"And then climb the mountain— "
"What's a mountain?" Again God explains.
"And near the top, you will find a cave— "
"What's a cave?" Again God explains.
"Inside the cave, you will find the woman. I want you to become one flesh with her and be fruitful and multiply— "
"How do I do all that?" Again God explains, and Adam sets out for the valley.
An hour later, Adam is back again and says, "God, I have another question."
"Yes Adam," replies God, rolling his eyes, "what is it this time?"
"What's a headache?"