[retroafroman]

I'm definitely an amateur at understanding biology, but having studied engineering; the inputs and outputs of the human body vary so widely that I have a hard time narrowing down one input to corresponding to one result.

When you think about the air you breathe, to the variety of things you ate (plus the additional microbiomes that inhabit the food, your skin, your gut, etc) it seems like we are just barely really understanding what the intakes to the body are.

Edit: here's a great point to start to think about it: https://youtu.be/bYOIhmZ0Osg?t=41m49s -watch for 10m