The Varna - asrama system and its current avatar - the Jati are probably the most (conveniently) misinterpreted and misunderstood beliefs affecting the Indian socio religious system.
The varna system that has been propounded is based on an individual’s profession, his merits and capabilities and it has its basis in the Vedic system.
The system finds mention in the three Vedas ( Rig Veda , Purusha Sukta 10.90.11-13, - which repeats in Yajurveda 31.10-11 and Atharva veda 19.6.506) .
What does the Purusha Sukta say ?
There are several versions of the Purusha Sukta. As per one version the sukta has 16 verses. As per another version there are 24 verses (the first 18 referred as Poorva narayana and the latter called the uttara narayana). This is the only hymn in the Rig Veda praising Purusha. Some authors hence are of the view that the entire Purusha sukta might itself be an interpolation in the Rig veda. Even considering the 24 verses, there is no mention of the words Vishnu or Narayana and it is surprising that this is considered a sukta praising Vishnu !
In the other Vedas too the numbering of these verses is different and depends on the version( which itself indicates that there is either a possibility of original material getting lost or addition of new material). (The Hymn is elaborated in Bhagavatha purana and Mahabharata )
Given the archaic nature of the old vedic language, it is very difficult to understand and properly interpret the real meaning of these verses. The translation given below is broadly based on the interpretation of two commentators – Bhatta Bhaskara and Sayana ( a commentator who lived in circa 1300 AD in the Vijayanagara kingdom and wrote along with his brother Madhava)
Following are some of the relevant verses that affect the topic under discussion.
mukham kimasya kau bahu
(Now some questions are raised by the sages:) When the gods decided to (mentally) sacrifice the Viratpurusha (and produce further creation), in how many ways did they do it? What became of his face or mouth? What became of his two arms? What became of His two thighs? What were (the products of) the two feet called?
bahu rajanyah kritaha
uru tadasya yadvaishyaha
padhyagam shudro ajayata
From His face (or the mouth) came the brahmanas. From His two arms came the rajanya (the kshatriyas). From His two thighs came the vaishyas. From His two feet came the shudras.
chandrama manaso jataha
chakshoh suryo ajayata
mukhad indrash chagnishcha
From His mind was born the moon. From His two eyes was born the sun. From His mouth were born Indra and Agni. From His breath was born the air.
nabhya asidanta riksham
shirshno dyauh samavartata
padhyam bhumirdishash shrotrat
tatha lokagamm akalpayan
From (His) navel was produced the antariksha (the space between the earth and the heavens). Dyuloka (or heaven) came into existence from His head. The bhumi (the earth) evolved out of His feet, and deek (or spacial directions) from His ears. Similarly (the demigods) produced the worlds (too).
More on the Purusha Sukta:
Nowhere in this sukta is a discrimination made between the four varnas. Further is clearly says that all the varnas came from a single cosmic being ( and as a natural corollary equal). If it were to be interpreted that the just because a varna came from higher position in the body – namely the face it becomes superior to the feet , how does one discriminate what came from the eyes and from the mind ? A subsequent verse also says that Bhumi evolved from his (Purusha’s) feet. Are we then to conclude that as the Sudras came from the feet and the Bhumi also came from the feet, all inhabitants on the bhumi are shudras ?
In fact it could properly be interpreted that no one class is superior to another and every class is needed for every other class’s survival. The entire hymn can probably be considered to signify the unifying presence of the Paramapurushan or can probably be considered to reiterate the fact that He is the primordial cause for all things to be there. It hence needs to be clearly interpreted for its philosophical meaning than for a biological one.