Sinrus, would that pre-Mycenian culture be the Minoan one?
Archaeological records are sparse but these suggest the Minoans worshipped goddesses, including (it's a very common one across cultures) a Mother Goddess of Fertility, which may have been conflated with the Mistress of Animals (another Minoan goddess apparently) to give the Mycenian Gaia.
Stress "may have been". I'm amazed at how all these things can be known at all. Last I checked the number of texts from the Minoan civilisation is very little. Their culture was assimilated into the Mycenian one through generations of oral transmission.
The Minoans lived on what today is called Crete, and were one of the first flourishing civilisations in Europe. For some reason (some say volcanic), they suffered a decline and were replaced by the Mycenians- but this "replacement" does not necessarily mean armed conflict, just stepping up when the place of top dog is not claimed anymore.
And one more thing. Zeus was god supreme, ok. But Gaia was still worshipped. The generational struggle of the Greek gods may be less about interethnic conflict and more about, who knows, the Oedipus complex.





