One such event is the fall of the Western Roman Empire in 476 AD. This event is often seen as the end of the classical world and the beginning of a new era, which was characterized by the rise of Christianity, the decline of urban life, and the increasing power of the feudal system.
Another key development that marked the beginning of the Middle Ages was the rise of the Germanic kingdoms in Europe. These kingdoms were established by the Germanic tribes who had migrated into the Roman Empire after its fall. The Germanic kingdoms were often unstable and in conflict with each other, but they also laid the foundation for the later development of European nations.
Finally, the Middle Ages are often seen as beginning with the spread of Christianity throughout Europe. Christianity became the dominant religion in Europe during this period, and it had a profound impact on the culture, politics, and society of the continent.
In conclusion, there is no single definitive answer to the question of when the Middle Ages started in Europe, but there are a few key events and developments that are often seen as marking their beginning. These include the fall of the Western Roman Empire, the rise of the Germanic kingdoms, and the spread of Christianity.