Chapter 6 of The Power of Myth by Joseph Campbell with Bill Moyers was mostly about the Goddess. Campbell talked about how most religions first worshiped a goddess. From the Goddess came the earth and from the earth came the food the people ate. As the cultures moved from agriculture to hunting and fighting other cultures for territory or animals, women were no longer as important. The women did the "less necessary" tasks of raising the children and tending the plants in small gardens or hunting for plants in the nearby land while the strong men went hunting and gaining more wealth and prestige for the clan or town. In most myths, as agriculture became less important than hunting or wars, a male deity overpowered the Goddess and often the Goddess seems forgotten or at war with the male deity. From what I learned looking at the small Wikipedia article on Gaia, the Greek mother goddess and considered to be Earth itself, she was never conquered. When Cronos killed Uranus, she became less popular, rather like the weak grandmother than an all powerful goddess. It did mention that oaths sworn in the name of Gaia remained the strongest oath a person could take for a long time. However, Campbell seemed to think that Hera was the Goddess, not Gaia, at least in this context. According to Wikipedia, Hera does seem to have been worshiped before Zeus was popular in Greece and beyond. I also recall a number of current fictional items (such as television shows) that are set in that time or speak of that time that refer to Hera and Zeus, or at least their cults, being at war with each other. As in most cultures the Goddess (Hera) and the conquering male deity (Zeus) eventually made peace and were worshiped equally (although the male deity became the "king" and the female merely his queen). In many cultures though, the male deity killed the Goddess and her body became the earth we live on and depend upon. Oddly enough Christianity (including the Muslim and Jewish variations in this context) never had a Goddess figure. As it spread, the faith destroyed all who worshiped the Goddess on the hills and destroyed her temples. Although a short arguemment could be made of the Mother Mary being similar to the Goddess in how she was worshiped, Campbell made a point of saying that the one religion (that split into three and more over time) is the only religion he knows of that has no Goddess figure that created the male deity that would destroy or devalue the Goddess.
Campbell also mentions that most ancient cities had their own deities that protected it. Although the city-states acknowledged and worshiped the other known deities around, it focused it's worship on one, maybe two deities. (The example that comes to mind is Athena and Athens.) He also talks about the older religions that thanked the animals themselves for giving their lives to be dinner and mentions that most religions have some sort of "rebirth". Most religions (Christianity included) strive to be dead to their animal nature or the desires of the flesh in order to be reborn to the desires of the spirit or universe. Commonly referred to as a "rebirth" or "enlightenment" the goal is common in most faiths.
Why do I bring all of these ideas to your attention? You are here to learn to write better stories, create better characters, and take people to other places known only in your mind at the moment. Why do you want to know about ancient myths in order to write science fiction? First of all, your setting may be on an alien planet that still lives in ancient times or your ship may go down on a planet that still believes in ancient gods and goddesses ruling according to their whims. More than likely, you will never write about prehistory times but it is important to remember that the future is built on the past. It is the ancient myths and religions of a culture that create rituals and holidays of the present. Just think about Christmas: the Catholic Church at the time wanted to stop a bloody celebration where people couldn't be punished for anything that happened in that week. Instead they changed the reason for the celebration and over centuries turned the bloody celebration into a warm and fuzzy time for memories while merging other rituals and traditions with the old Roman holiday. (Here is an interesting article I found on origins of Christmas and the accompanying traditions. Caroling anyone?)
Events and rituals of the past or of today create the culture and society of the future and knowing the origins of a few of the customs your characters encounter, being able to tell the story of the history or significance of a cultural event or item can make your culture and story come alive for your readers.