The concept of the First Ancestor Civilization (also referred to as the First Ancestor Race) is a recent addition to Evangelion lore, introduced in the 2003 PlayStation 2 video game Neon Genesis Evangelion 2. Despite some reservations by fans, the concept is not new, and has simply never been a focus of the Anime series.
The First Ancestor Civilization is an ancient extra-terrestrial race (possibly highly-evolved humanoid), who are responsible for the creation of the Angels and the Lilim. Or more accurately, they are responsible for the creation of the White Moon and the Black Moon, which are actually artificial carriers of life (or seeds of life) that their civilization spreads across the universe. Although their motive for doing so is unknown, the idea of propagating life across the universe is not an uncommon one (even among a race as young as mankind).
Simple coincidence (and possibly bad luck) is blamed for two such seeds to have landed upon the same planet, which in turn causes the conflict between Adam and Lilith-based life forms. This also explains why the Angels and the Lilim are described as simply different directions life may have taken (as explained by Misato Katsuragi in The End of Evangelion), because their source/base DNA is one and the same. From a human perspective, the First Ancestors may therefore seem Godly.
Based on Neon Genesis Evangelion 2 for PlayStation 2