Three engineering students were gathered together

Three engineering students were gathered together discussing who must have designed the human body. 

..One said, "It was a mechanical engineer. Just look at all the joints." 

..Another said, "No, it was an electrical engineer. The nervous system has many thousands of electrical connections." 

....The last one said, "No, actually it had to have been a civil engineer. Who else would run a toxic waste pipeline through a recreational area?"