In later Vedic phase, striking changes took place in the Varna System. There was an increase in the privileges of the two higher classes, the Brahmanas and the Kshatriyas at the cost of the Vaisyas and Sudras.  

• In the Panchavimsa Brahmana, the Kshatriya is placed first, higher than the Brahmana but in the Satapatha Brahmana, the Brahmana is placed higher than Kshatriya.  
• In later Vedic society the importance of the purohita (priest) is stressed, as mentioned in the Vedic texts.  
• The Kshatriyas challenged Brahmanical supremacy and their exclusive privilege of entering the asramas, a regulated four stage life namely brahmacharya, grihasta, vanaprastha and sanyasa.  
• The outcome of this was the birth of Jainism, Buddhism and Ajivakam. 

Source: Tamil Nadu state board.