An chemical engineer, an electrical engineer and a civil engineer
An chemical engineer, an electrical engineer and a civil engineer are discussing the human body and the nature of God.
"Look at the body," says the chem-e, "and it's plain that God is a chemical engineer. The elegance of the circulatory system in carrying oxygen, the efficacy of the liver in filtering toxins, the brute power of the stomach in dissolving food and converting it to fuel. It's obvious!"
"Wrong," counters the EE, "God is an electrical engineer. Look at the brain…the world's most sophisticated computer. Look at the nerves, carrying electrical signal with such efficiency. See how the muscles repond with grace and precision. It's obvious!"
The civil engineer considers for a moment, and says "You're both wrong. God is a civil engineer, because only a civil engineer would run a waste disposal line through a great recreational area."