As it says in the forward to the Joel Chandler Harris book I received today:
"Tracing the origin of these tales seems almost impossible. Some are known widely in the old World. For example, the sham sickness of Brer Rabbit when he persuaded Brer Fox to carry him is known in the folktale traditions of Germany, Esthonia, Finland, Lapland, Denmark, Sweden and Russia. In Europe it was the fox, not the rabbit, who was the trickster hero. The Tar-Baby tale, however, seems to be of African origin: Kaffir, Rhodesia, Hottentot."