The primary difference between the early and later Vedic civilizations of India was the development of the caste system.
The Vedic people were Aryans who migrated into India c. 1500 - 500 c.e. The name Vedas in the Aryan dialect meant "wisdom" or "knowledge." The name originates from the "rig veda" a collection of sacred works from the time period.
Originally, the Aryan people of India were organized into local chieftains which consisted of communities of herdsmen and farmers. As their population grew, their political structure gradually evolved as well as their social structure. As part of that social structure, ones role in society became defined by ones occupation. This structure evolved into the caste system. By the year 1000 c.e., there were four recognized castes, or varnas: The Brahmins, (Priests); kshatriyas, (warriors and aristocrats); vaishas, (farmers, artisans and merchants); and shudras, (landless peasants and serfs.) Eventually, those who performed undesirable tasks such as tanning, burying the dead, and butchering animals were considered members of a fifth class known as the 'untouchables." This development of the caste system marked the difference between the earlier and later Vedic age.