Archaeologists have found evidence of pre-Greek worship of a god on site long associated with Zeus worship:
But archaeologists say they have now found the ashes, bones and other evidence of animal sacrifices to some pre-Zeus deity on the summit of Mount Lykaion, in the region of Greece known as Arcadia. The remains were uncovered last summer at an altar later devoted to Zeus.
Fragments of a coarse, undecorated pottery in the debris indicated that the sacrifices might have been made as early as 3000 B.C., the archaeologists concluded. That was about 900 years before Greek-speaking people arrived, probably from the north in the Balkans, and brought their religion with them.
The excavators were astonished. They were digging in a sanctuary to Zeus, in Greek mythology the father of gods and goddesses. From texts in Linear B, an ancient form of Greek writing, Zeus is attested as a pre-eminent god as early as 1400 B.C. By some accounts, the birthplace of Zeus was on the heights of Lykaion.
After reviewing the findings of pottery experts, geologists and other archaeologists, David Gilman Romano of the University of Pennsylvania concluded that material at the Lykaion altar “suggests that the tradition of devotion to some divinity on that spot is very ancient” and “very likely predates the introduction of Zeus in the Greek world.”