Tech Tree
The Tech Tree has been overhauled and expanded for the timeframe. At the beginning, eastern and Islamic civs start with a fair portion of the tech tree uncovered, while the western civs have to rediscover many technologies.
The endpoint of the tech tree, Industrial and Social Revolution, represents the massive changes Europe underwent at the turn of the century as a result of the French Revolution and the start of the industrial revolution in England. Not all civilizations will be able to reach the end of the tech tree within the allotted time.