Simplify the following text for a Grade 13 native English-speaking person.
Original: The development of the vassal , in a society that was increasingly organised around the concept of `` lordship '' -- in French the seigneur -- is one sign that Antiquity ended and the Early Middle Ages began .
Simplified: Feudal society was increasingly based on the concept of `` lordship '' -- in French the seigneur -- which was one of the distinguishing features of the Early Middle Ages which evolved out of Late Antiquity .