Did you know:
Hide skins were usually "tanned" by taking the skin off of the animal, and rubbing-in an oil made from boiled brains of the animal and campfire ashes. The mixture of brain matter and lye from the ashes creates a chemical preservative that turns the animal hide into leather. Every mammal on earth has a brain size that is exactly proportionate to the amount of skin on its body. Meaning, that there is exactly the right amount of brain matter to tan all of the skin on each individual mammal.