Original sentence: Kurdish has in turn emerged as a group within Northwest Iranian during the Medieval Period (roughly 10th to 16th centuries).Kurdish is a language of the Northwestern Iranian group which has likely separated from the other dialects of Central Iran during the early centuries AD (the Middle Iranian period).The Kurdish people are believed to be of heterogeneous origins combining a number of earlier tribal or ethnic groups including Lullubi, Guti, Cyrtians, Carduchi
Edited sentence: The Kurds emerged as a group within Northwest Iran during the Medieval Period (roughly 10th to 16th centuries AD)  and are believed to be of heterogeneous origins combining a number of earlier tribal or ethnic groups including Lullubi, Guti, Cyrtians, Carduchi