A bit soiled from years in and out of dumpsters, but...
Three engineers are dicussing God.
Chemical Engineer: He must have been one of us. When you get down to it, it's all amino acids and chemical reactions.
Electrical Engineer: No, no. He must have been an electrical engineer. Messages are sent around the body by electrical impulses, brain synapses, muscle function, all of it.
Civil Engineer: Nah, nah. Definitley civil. You try organizing so many things to provide so much simultaneous function.
Chemical Engineer: Actually, I think he's correct. Only a Civil Engineer would run a waste water facility right through the middle of an amusement park.
..and so he hobbled forward...