Final answer:
Christianity spread from the eastern Mediterranean through the Roman Empire, was influenced by state adoption, and expanded worldwide during the Age of Exploration. The rise of Protestantism and subsequent Catholic Counter-Reformation shaped Europe's religious landscape. Early spread is represented on historical maps.
Step-by-step explanation:
The spread of Christianity from its founding until 2012 can be traced through a variety of historical events and processes. Christianity, which began as a Jewish sect in the eastern Mediterranean, rapidly spread through the Roman Empire due to various factors, including the missionary efforts of the Apostles and an initially tolerant Roman policy towards new religions. Conversion of Constantine and the subsequent adoption of Christianity as the state religion under Theodosius I further cemented its spread in Europe.
During the Age of Exploration, Christianity, especially in its Catholic form, was spread to other parts of the world by European colonizers and missionaries such as the Jesuits. This was often intertwined with colonial expansion, with missionaries arriving in territories alongside traders and colonizers. The emergence of Protestantism in the 16th century led to religious reforms and the subsequent Wars of Religion, which altered the religious landscape in Europe. The Catholic Church responded with the Counter-Reformation, implementing reforms and reaffirming Catholic doctrine.
The map mentioned, representing the early spread of Christianity, showcases its expansion throughout the Mediterranean, including northern Africa, highlighting how it became a dominant faith across various cultures and empires from the first through the sixth centuries.