The silk roads are called trans-eurasian because they

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.  

these civilizations were located around fertile rivers, where they could produce an abundance of crops