One day God came to Adam to pass on some news.  "I've got some good
news and some bad news", God said.  Adam looked at God and said, "Well, give
me the good news first."  Smiling, God explained, "I've got two new organs
for you.  One is called a brain.  It will allow you to be very intelligent,
create new things, and have intelligent conversations with Eve.  The other
organ I have for you is called a penis.  It will allow you to reproduce your
now intelligent life form and populate this planet.  Eve will be very happy
that you now have this organ to give her children."

Adam, very excited, exclaimed, "These are great gifts you have given to
me.  What could possibly be bad news after such great tidings?"  God looked
upon Adam and said with great sorrow, "The bad news is that when I created
you, I only gave you enough blood to operate one of these organs at a time."