The origin of caste cannot be traced to an exact point of time or source . There are various theories which deal with origin of caste system in India .

I. Traditional theory

According to this theory, the caste system is of divine origin. It says the caste system is an extension of the varna system, where the 4 varnas originated from the body of Bramha.
At the top of the hierarchy were the Brahmins who were mainly teachers and intellectuals and came from Brahma’s head. Kshatriyas, or the warriors and rulers, came from his arms. Vaishyas, or the traders, were created from his thighs. At the bottom were the Shudras, who came from Brahma’s feet. The mouth signifies its use for preaching, learning etc, the arms – protections, thighs – to cultivate or business, feet – helps the whole body, so the duty of the Shudras is to serve all the others. The sub-castes emerged later due to intermarriages between the 4 varnas.
The proponents of this theory cite Purushasukta of Rigveda, Manusmriti etc to support their stand. In ancient India, various sub-castes were born out of these castes and this has received a classical interpretation in the account of Manu. The theory has been criticized for its being a supernatural theory and for its base being just divine.

II.Political theory/Brahmanical theory

 According to this theory, the Brahmins wanted to have a full control over the society in order to curb and rule them. So, their political interest created a caste system in India.  Abbe Dubois, a French scholar, originally put forward this theory that was also supported by Indian thinkers such as Dr. Ghurye.

III.Religious theory

It is believed that various religious customs had given a birth to the caste system in India. People connected to religion like Kings and Brahmins were given higher positions. Different people used to perform different tasks for the administration of the ruler that later on became the basis of caste system.

Along with this, restriction on food habits had led to the development of caste system. Earlier there were no such restrictions on taking food with others as people used to believe their origin was from one ancestor. But as they started worshipping different Gods, their food habits changed. This laid the foundation of caste system in India.

IV. Occupational theory

Nesfield originally gave the name  occupational theory, according to which castes in India developed as per the occupation of a person. Concept of superior and inferior caste also came with this as some persons were doing superior jobs and some were into lower kinds of jobs. All those people who were doing the task of purohits were superior and they were the ones who used to do specialization. Superior caste with time grouped into Brahmins. Similarly, other groups were also formed leading to different castes in India.

V. Evolutionary theory

According to Denzil Ibbesten Caste system is just like other social institution and developed through the process of evolution.Factors which contributed to it were purity of blood, devotion to a particular profession,theory of karma, conquests of one army by the other , geographical location and isolation.

According to this theory, the caste system did not come into existence all of a sudden or at a particular date. It is the result of a long process of social evolution.

• Hereditary occupations;
• The desire of the Brahmins to keep themselves pure;
• The lack of rigid unitary control of the state;
• The unwillingness of rulers to enforce a uniform standard of law and custom
• The ‘Karma’ and ‘Dharma’ doctrines also explain the origin of caste system. Whereas the Karma doctrine holds the view that a man is born in a particular caste because of the result of his action in the previous incarnation, the doctrine of Dharma explains that a man who accepts the caste system and the principles of the caste to which he belongs, is living according to Dharma. Confirmation to one’s own dharma also remits on one’s birth in the rich high caste and violation gives a birth in a lower and poor caste.
• Ideas of exclusive family, ancestor worship, and the sacramental meal;
• Clash of antagonistic cultures particularly of the patriarchal and the matriarchal systems;
• Clash of races, colour prejudices and conquest;
• Deliberate economic and administrative policies followed by various conquerors
• Geographical isolation of the Indian peninsula;
• Foreign invasions;
• Rural social structure.

VI. Manu theory 

Professor Hutton propounded this theory. The caste system was there in India before Aryans but Aryans made caste system clearer by enforcing this on everybody. In India, there was a fear of touching or coming in contact with strangers as touching might lead to either good or bad. So people started restraining themselves from others and this gave rise to restrictions regarding eating habits.

VII. Racial theory of Caste

Herbert Risley proposed that caste came into existance due to clash of  cultures and contact of races. This theorey was also supported by Ghurye, Majumdar, Westermark and others.

The Sanskrit word for caste is varna which means colour. The caste stratification of the Indian society had its origin in the chaturvarna system – Brahmins, Kashtriyas, Vaishyas and Shudras. Indian sociologist D.N. Majumdar writes in his book, “Races and Culture in India”, the caste system took its birth after the arrival of Aryans in India.

Rig Vedic literature stresses very significantly the differences between the Arya and non-Aryans (Dasa), not only in their complexion but also in their speech, religious practices, and physical features.

The Varna system prevalent during the Vedic period was mainly based on division of labour and occupation. The three classes, Brahma, Kshatra and Vis are frequently mentioned in the Rig Veda. Brahma and Kshatra represented the poet-priest and the warrior-chief. Vis comprised all the common people. The name of the fourth class, the ‘Sudra’, occurs only once in the Rig Veda. The Sudra class represented domestic servants.

Risley mentioned 6 processes of development of caste system

1. Change in traditional occupation
2. migration
3. customary changes
4. preservation of old practices
5. tribals getting into folds of Hinduism
6. Role of religious enthusiasts.-creation of sects by preaching their own ideology. example Kabir Das

VIII. Theory of cultural integration:

Proposed by Sarat Chandra Roy ,caste is an outcome of the interaction between the Indo Aryans ,varna system on one hand and the tribal system of the Dravidian on the other.

It is believed that caste system in India is not a result of one individual theory or factor but this is the result of several factors.