Bundahishn
On the nature of the ape and the bear they say, that Yim, when reason (nismô) departed from him, for fear of the demons took a demoness as wife, and gave Yimak, who was his sister, to a demon as wife; and from them have originated the tailed ape and bear and other species of degeneracy.
This, too, they say, that in the reign of Az-i Dahâk a young woman was admitted to a demon, and a young man was admitted to a witch (parik), and on seeing them they had intercourse; owing to that one intercourse the black-skinned negro arose from them.
When Frêdûn came to them they fled from the country of Iran, and settled upon the sea-coast; now, through the invasion of the Arabs, they are again diffused through the country of Iran.