How did the Aryan concept of varna (social class) evolve over time, and what social roles and responsibilities were associated with each varna?

The concept of varna evolved from occupational categories to hereditary social classes, known as Brahmins (priests), Kshatriyas (warriors), Vaishyas (merchants and farmers), and Shudras (laborers). Each varna had specific duties, privileges, and restrictions based on birth and occupation.