Strabo says the oracle was established by the Pelasgians, which may mean pre-Achaean and prehistoric. In Book II, Herodotus calls the priests who interpret the sounds doves. He also says that a black dove settled on the sacred tree, declared in human words that the tree was to be the oracular site:
[T]he latter settled on an oak tree, and there uttered human speech, declaring that a place of divination from Zeus must be made there; the people of Dodona understood that the message was divine, and therefore established the oracular shrine.The oracle at Dodona is also mentioned in the Odyssey XIV:
But Odysseus, he said, had gone to Dodona, to hear the will of Zeus from the high-crested oak of the god, even how he might return to the rich land of Ithaca after so long an absence, whether openly or in secret.and in Plato's Phaedrus:
They used to say, my friend, that the words of the oak in the holy place of Zeus at Dodona were the first prophetic utterances.Archaeologists have uncovered buildings only dating back to the 4th century B.C. to which King Pyrrhus added other facilities, including a theater, the following century.
"The Oracle of Dodona," by D. M. Nicol. Greece & Rome, 2nd Ser., Vol. 5, No. 2. (Oct., 1958), pp. 128-143.