New Tech Prerequisites

[Yxklyx]

In order to research a new technology do you just need to have the immediate prerequisites or do you also need to have everything else that comes before it?

[Flubber]

My experience is that all predecsor techs are NOT required if you have the two immediate prereqs. However, the game may sometimes only give you a choice of some of those "unnecessary " techs to research . I find you can only skip the lower techs for so long before you get a turn where they are the ONLY research options