Complex sentence: In the 1st century BC, the expanding Roman Republic absorbed the whole Eastern Mediterranean area (which included much of the Near East) and under the Roman Empire the region was united with most of Europe and North Africa in a single political and economic unit.
Split into simpler sentences: In the 1st century BC, the expanding Roman Republic absorbed the whole Eastern Mediterranean, which included much of the Near East. The Roman Empire united the region with most of Europe and North Africa in a single political and economic unit.