Complex sentence: The Indo-Aryan Migration theory posits a migration of Indo-European-speaking people the Pontic Steppes into Europe, the Levant, south Asia and east Asia.
Split into simpler sentences: The Indo-Aryan Migration theory is part of the Indo-European migration theory. It posits a migration of Indo-European-speaking people the Pontic Steppes into Europe, the Levant, south Asia and east Asia.