Although its exact origins are lost in time, Greek religion is thought to date from about the period of the Aryan invasions of the 2d millennium B.C. Those invaders encountered two other peoples who had existed in the region of Greece from Neolithic times: the Aegeans (Pelasgians) and the Minoans of Crete. The Aryans fused with the Aegean and Minoan cultures to create what is now considered Greek culture. The result, known as the Minoan-Mycenean civilization, flourished in the period from 1600 B.C. to 1400 B.C.
Previous to the invasions, the Helladic communities had been widely separated geographically, but the attacking foreigners swept everything along in their path, including various beliefs that were prevalent in the outlying districts. At first the result was a confused conglomeration, but gradually a certain systematization of the gods began to take place. The marriage of Zeus, a sky god of the conquerors, and Hera, a fertility goddess of the conquered, symbolized the attempt at fusion, although the constant conflict between the divine pair, as seen in the Iliad, indicates the tensions of the match. The classical Greek pantheon was peopled with gods from all the cultures involved: Zeus the sky father, Demeter the earth mother, and Hestia, the virgin goddess of the hearth, were borrowed from the Indo-European invaders; Rhea was an indigenous Minoan goddess; Athena was Mycenean; Hera and Hermes were Aegean; Apollo was Ionian; Aphrodite came from Cyprus and Dionysus and Ares from Thrace.