It really depends on what you mean by individualism. If you confine it to the specific idea that permeated throughout the Enlightenment then yes I would be inclined to say that it was developed there. However, plenty of philosophical elements of individualism can be found in ancient philosophy, particularly in the ancient Chinese tradition. Zhuangzi is one such example. His philosophy revolves around self-cultivation, although it contains Daoist elements which may appear to defy individualism as the Enlightenment sees it. Check this website out if you wish to know more about individualism in Chinese thought.