Varna or colour was the basis of initial differentiation between the Vedic and non-Vedic people. Rig-Veda describes arya varna and dasa varna. With gradual change in the society and religion, the Rig Vedic period categorises the society into varnas depending on one’s profession and within a family, members could follow the profession of different varnas. However, in later Vedic period, varnas came to be birth-based rather than profession-based. The 10th mandal of rigveda, known as ‘purush sukta’ defines that the varnas are produced from different parts of the body of the God as Brahmin from the mouth, kshatriya from arms, vaishya from thighs and shudra from feet. However, many scholars believed that 10th Mandal to RigVeda was added in later vedic period in order to suppress the Sudras.
The four fold social categorizations that have been set out within the Purush-sukta define the distinctive set of duties and functions to be performed according to Dharmashastra. The Brahmins were assigned the highest status of the four varnas entrusted with maximum responsibilities. The entire task of preserving Dharma was mainly the responsibility of the Brahmin. The next social status in Varna hierarchy was given to the Kshatriya’s, includes soldiers, generals and kings had the responsibility of defending the nation in times of war and administering law and order in the society. The Vaishya’s were agricultural and cattle raisers. They also carry out trading activities. The sudras were assigned with lower status as servants to the other three castes, the sudras performed many of the tasks that involve "pollution," such as agricultural labour, leather working, disposing of garbage, and laundering.
The Sudra’s gradually came to be so much looked down upon that they could not touch a Brahmin and also they could not be initiated into the Vedic study. Over the course of period this Varna system became so rigid and deeply rooted in society that resulted to the untouchability. The sudras were considered to be polluted hence they became untouchables.