is there a way i can stop the game from moving to the next era? for example i don't want technology to proceed past the "ancient era" or "classical era." i want all civs to be stuck in the same time period and be unable to advance.

i realize i can remove certain resources from the map and that will prevent some units from being built, however not all units require a special resource to be built many just require a certain tech.

does anyone have any great ideas on this one?