Theology Behind the Castes
Reincarnation is the process by which a soul is reborn into a new material form after each life; it is one of the central features of the Hindu cosmology. Souls can move not only among different levels of human society but also into other animals. This belief is thought to be one of the primary reasons for the vegetarianism of many Hindus.
Within a single lifetime, people in India historically had little social mobility. They had to strive for virtue during their present lives in order to attain a higher station their next time around. In this system, a particular soul's new form depends upon the virtuousness of its previous behavior. Thus, a truly virtuous person from the Shudra caste could be rewarded with rebirth as a Brahmin in his or her next life.
Daily Significance of Caste
The three key areas of life historically dominated by caste were marriage, meals, and religious worship.
Marriage across caste lines was strictly forbidden. Most people even married within their own sub-caste or jati.
At mealtimes, anyone could accept food from the hands of a Brahmin, but a Brahmin would be polluted if he or she took certain types of food from a lower caste person. At the other extreme, if an untouchable dared to draw water from a public well, he or she polluted the water, and nobody else could use it.
In religious worship, Brahmins, as the priestly class, presided over rituals and services including preparation for festivals and holidays, as well as marriages and funerals. The Kshatriya and Vaisya castes had full rights to worship, but in some places, Shudras (the servant caste) were not allowed to offer sacrifices to the gods. Untouchables were barred entirely from temples, and sometimes they were not even allowed to set foot on temple grounds. If the shadow of an untouchable touched a Brahmin, the Brahmin would be polluted, so untouchables had to lay face-down at a distance when a Brahmin passed.
Caste among Non-Hindus
Curiously, non-Hindu populations in India sometimes organized themselves into castes as well. After the introduction of Islam in the subcontinent, for example, Muslims were divided into classes such as the Sayed, Sheikh, Mughal, Pathan, and Qureshi. These castes are drawn from several sources: The Mughal and Pathan are ethnic groups, roughly speaking, while the Qureshi name comes from the Prophet Muhammad's clan in Mecca.
Small numbers of Indians were Christian from around 50 CE onward. Christianity expanded in India after the Portuguese arrived in the 16th century. Many Christian Indians continued to observe caste distinctions, however.
The British Raj and Caste
When the British Raj began to take power in India in 1757, they exploited the caste system as a means of social control. The British allied themselves with the Brahmin caste, restoring some of its privileges, which had been repealed by the Muslim rulers.
Caste Relations in Independent India
The Republic of India became independent on August 15, 1947. India's new government instituted laws to protect the "Scheduled castes" and tribes which included both the untouchables and groups living traditional lifestyles. These laws include quota systems that help to ensure access to education and to government posts. Because of these shifts, a person's caste has become somewhat more of a political category than a social or religious one in modern India.
Reference
Szczepanski, K. (2019). What to Know About India's Caste System. [online] ThoughtCo. Available at: https://www.thoughtco.com/history-of-indias-caste-system-195496 [Accessed 2 Oct. 2019].