It seems as if there are etymological roots, as Faldage points out, and conceptual roots, as perhaps OPT is pointing to.
Under conceptual roots, I can see birth, life, death, eat, poop, copulate, love, hate, sleep, hurt, see, hear, feel, taste, smell, fight, play, walk, etc. kind of topping the list. But an agrarian society is going to have a somewhat different set of roots (pardon the pun) from a hunter-gatherer society.
edit: Or is the idea that if you go back far enough you combine etymological and conceptual roots?