The title is a bit over dramatic but, per the title, if you could contribute with one piece of knowledge to a book that every single individual should learn from in order to kickstart a civilization, what would be yours?
My personal choice would be the process of soap making, from scratch.
Today I watched someone in an airport rinse one of their hands while holding a bag handle in the other. Then they struggled to get a paper towel for their shit covered hand as they walked out of the bathroom.
We are fucked if we slip even a little, lol. People even know about germs these days and still only go through the gesture of washing without understanding why.