This is a good question. God was originally female because the male role in reproduction was not known, and women were the ones giving life. This is where Gaia, the Mother Earth, came from. The problem with a female god is that it led to a lot of sacrifice for a variety of reasons, so it wasn't a peaceful god. The Romans innovated by making the father the patriarch of the family, then the Persians and the Hebrews invented the masculine God. Then Christ came, and the unstable chaotic matriarchy became a patriarchy. See Sylvain Durain's The End of the Sacred for more details.