Complex sentence: The history of glass-making can be traced back to 3500 BC Asia in Mesopotamia, however, they may have been producing second-rate copies of glass objects from Egypt, where this complex craft actually originated.
Split into simpler sentences: The history of glass-making can be traced back to 3500 BC Asia in Mesopotamia. However, they may have been producing second-rate copies of glass objects from Egypt, where this complex craft actually originated.