Complex sentence: Syriacs, Chaldo-Assyrians, Nestorians and Chaldeans (see names of Syriac Christians), are a distinct ethnic group whose origins lie in northern Mesopotamia, what was Assyria.
Split into simpler sentences: Syriacs, Chaldo-Assyrians, Nestorians and Chaldeans (see names of Syriac Christians). They are a distinct ethnic group whose origins lie in northern Mesopotamia, what was Assyria.