The Story of Oannes
"At first they led a somewhat wretched existence and lived without rule after the manner of beasts. But, in the first year appeared an animal endowed with human reason, named Oannes, who rose from out of the Erythian Sea, at the point where it borders Babylonia. He had the whole body of a fish, but above his fish's head he had another head which was that of a man, and human feet emerged from beneath his fish's tail. He had a human voice, and an image of him is preserved unto this day. He passed the day in the midst of men without taking food; he taught them the use of letters, sciences and arts of all kinds. He taught them to construct cities, to found temples, to compile laws, and explained to them the principles of geometrical knowledge. He made them distinguish the seeds of the earth, and showed them how to collect the fruits; in short he instructed them in everything which could tend to soften human manners and humanize their laws. From that time nothing material has been added by way of improvement to his instructions. And when the sun set, this being Oannes, retired again into the sea, for he was amphibious. After this there appeared other animals like Oannes."
An account rendered by Berossus, a Babylonian priest of the 13th century B.C.