In civ5 you can access the tech tree which gives you a long term access of all thechnoliegies.
Well this tech tree is sort of messed up.
For example the technology nano technology seams to be in the ancient era and the wheel sits humbly in the industrial era.
Bcause the tech tree means also that the technoly choosing is also messed up. You know when you start the game and settel your city you get a tech panel and shows you starting technoliegies wel in first position sits steam power?