By what means other than formal amendment has constitutional change occurred

One of the major ways in which constitutional change has occurred outside of the official amendment process is through the judiciary, which different generations of judges ruling differently based on "evolving" and more progressive interpretations of the Constitution. 

The Protestant Reformation's started in 1517, disturbing the religious and political order in Europe´s Catholic countries. The outcome was the European wars of religion prosecuted in Europe in the 16th, 17th and part of the 18th century. Nonetheless, uprisings, territorial disputes, and Great Power conflicts were also causes of the wars.