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.
My contribution is a very practical tip for parents: When you need to carry a kid sitting on your shoulders, first pick them up and have them sit with both legs on your right shoulder. Then, with your right hand, grab the kid’s right leg, and with your left hand grab the kid’s left leg and lift it over your head to place it in your left shoulder. Mirror the maneuver if necessary. The result is a quick lift-sit-and-switch technique, and fewers kicks to the head.