This is another informative link on original caste system in ancient India
Hindu Wisdom - Caste_System
Sage Valmiki, the celebrated author of of the epic, Ramayana, was a low caste hunter. He came to be known as a Brahmin sage on the basis of his profound knowledge of the scriptures and his authorship of the Ramayana.
Sage Aitareya, who wrote the Aitareya Upanishad and was born of a Shudra woman.
Rishi Parashar, the famous law-giver was the son of a Chandala, the lowest of the Sudras.
Rishi Vasishta, was the son of a prostitute, but honored as a sage.
Sage Vidura, a Brahmin sage who gave religious instruction to Kind Dhritarashtra, was born to a low caste woman servant of the palace. His caste as a Brahmin sage was determined on the basis of his wisdom and knowledge of Dharma Shastras (scriptures).
The
Kauravas and
Pandavas were the descendants of Satyavati, a low caste fisher-woman, and the sons of Sage Vyasa. Vyasa's father was the Brahmin Sage Parasara, the grandson of Sage Vasishtha. In spite of this mixed heredity, the Kauravas and Pandavas were known as Kshatriyas on the basis of their occupation.
Chandragupta Maurya was from the Muria tribe, which used to collect peacock (mor) feathers;
Samrat Ashok was the son of a daasi.
Saint Thiruvalluvar who wrote Thirukural was only a weaver. Other saints were adored including
Kabir,
Sura Dasa,
Ram Dasa and
Tukaram came from the humblest class of Hindu society.
), the caste system is not a rigid one when it started. 
