The emergence of law is lost in prehistory. Written laws appear as soon as writing appears in a culture. But law, in the sense of an organized use of coercion based upon an edict by a head person, was clearly in operation long before writing arrived. Robert Murdock's Ethnographic Atlas, University of Pittsburg Press (1967) lists data on 862 preliterate cultures. About two thirds of them had private ownership of real property that was governed by rules of descent that determined the flow of ownership from one generation to the next. Those rules were not self-executing. They required systematic implementation by the group.

Long before there was Greek or Latin, the language from which they evolved, called Indo-European, contained the root ("leg-") from which our words for law, legal, legislate, and so on was derived, and the root ("jewo-") from which judge, justice, jury, judicious, adjudicate, and so on were derived. You can see in these words early signs of the two domains that would later emerge in law, the domain of positive law, from "leg-" that which is listed or announced, as in a law or a piece of legislation, and the moral law, from "jewo-" that which is just or judicious.
Written law emerged in China with the Xia Dynasty (2100-1600 B.C.). The Xia kingdom was a feudal system of social classes where the law established the obligations of the classes. It seems likely that law was the premier contribution of these early regimes.