I've noticed that many races seem to be getting ahold of Warp Drive IV very early in the game, yet none of them have any of the prerequisite techs. I've played all those races, so I know it isn't one of their tech trees. However, I do notice that the minor races have this technology in the same fashion, even though they have precious little bargaining power to procure it!
I suspect that the default tech tree has a bug that gives early, possibly quite cheap access to Warp Drive IV, and the major races are trading for it with the minors.