Simplify the following text for a Grade 13 native English-speaking person.
Original: Thus , the major peculiarities of the ancient Greek political system were ; firstly , its fragmentary nature , and that this does not particularly seem to have tribal origin ; and secondly the particular focus on urban centres within otherwise tiny states .
Simplified: Thus , the major peculiarities of the Ancient Greek political system were ; firstly , its fragmentary nature ; and secondly the focus on urban centres within otherwise tiny states .