Biologically speaking, humans are a tube-in-tube system. Our tube called skin holds all tubes together. Our blood runs in tubes through the whole body. You put water into a tube at the top and it comes out through a tube at the bottom. The same with food, only different tube. You put a tube into a female tube as a man and after 9 months a new tube system comes out of the woman through a really fat tube.
The history of the tube maintenance goes on and on. Simply input and output. Nothing complicated. The whole life is nothing but tube maintenance.
– Loosely quoted after Brad Blanton