Answer: Social classes.
Specialization is a process by which a certain group of people dedicate their time to only one craft. This was possible in large settlements that produce a constant surplus of food. With this change, groups of farmers, blacksmiths, merchants, etc., were able to specialize in these specific areas.
As jobs were divided, social classes arose as well. Social class refers to a model of social stratification in which people are ranked in a hierarchy of social categories.