Caste system

It is a fact that more than 70 per cent of the ancient Hindu Rishis, or enlightened masters of India, belonged to the lower castes.
Valmiki and Vyasa , who wrote the epics Ramayana and Mahabharatha respectively, belonged to the lower castes.
In ancient times , one's caste was determined by one's temperament, talents and inclinations. Caste was not a barrier to the lower caste people, who rose to the level of the upper castes through their talents.
This was the reason why Kshatriyas like the Buddha and Vishwamitra , became Brahmins or men of spiritual nature and why a Brahmin like Parashurama became a Kshatriya.
This is also the reason why shudras or low caste people like Valmiki , Vyasa, Vasishtha, Narada, Drona, Karna ,Thiruvalluvar were raised to the position of a Brahmin or Kshatriya , in virtue or their superior learning or valour.
Much more of this information can be found in Sri Sri Ravi Shankar's book"Heritage of the dalits".
Shankaracharya and others , were the great caste-makers. They would sometimes get hordes of Baluchis and at once make them Kshatriyas, and also get hordes of fishermen and make them Brahmins forthwith.
It was with the advent of the foreign invasions in India, that the caste system became rigid, and migration of people to different castes were stopped.
Even then, enlightened masters from the lower castes such as Kabir, Ravi Das, Sri Narayana guru were revered by the upper castes as well.
When India gained independence due to the efforts of Hindus like Gandhi, perfect equality was thrust upon the masses of India , no matter to what caste one belonged to, thus reestablishing and continuing the ancient tradition of India.
Even the constitution of independent India , was created bya Dalit called B.R.Ambedkar.
It will take some time for the deadweight of tradition of the rigid caste system to be removed from India. But as enlightened Hinduism and Buddhism, as preached by Gandhi, Swami Vivekananda, Ramakrishna Paramahamsa, Sri Sri Ravi Shankar and others are reaching the masses, slowly these shackles are being dissolved .