One day God came to Adam for a brief discussion. "I've got some good news and some bad news." God said.
Adam looked thoughtfully at his maker and replied, "Please give me the good news first."
Smiling, God explained, "I've created two new organs for you. One is called a brain. This organ will allow you to be very intelligent, create new things, and carry on productive conversations with Eve. The other organ is called a penis. It will allow you to reproduce your intelligent life form and begin populating the planet. Eve will be very pleased that you are now equipped with this organ as she will be able to conceive children."
Adam, very excited, exclaimed, "These are great and wonderful gifts you have given me. What could possibly be bad news after such great tidings?"
God then looked upon Adam, and said with great sorrow, "The bad news is I only gave you enough blood to operate one of these organs at a time."