The Eleusinian Mysteries and Other Mystery Religions by Jeremy Naydler, Ph.D.

The Eleusinian mysteries were celebrated from at least the eighth century B.C. at Eleusis, near Athens, and continued into the Hellenistic period. While there is some reason to believe that they were established at a much earlier date—in the second half of the fifteenth century B.C.—and that their origin was Egyptian, neither an earlier dating nor an Egyptian origin is accepted by the majority of scholars today, for lack of firm evidence. Nevertheless, the possibility of an earlier Egyptian origin of the Eleusinian mysteries should not be dismissed out of hand, and there are some who have no difficulty with this view. But whether or not they had an Egyptian origin
is a side issue to the present argument. Eleusis was just one of many mystery centers that flourished throughout the Greek and Greco-Roman world.