I will not discuss here the Purusha Sukta (10.90) of the RgVeda in details, but try to raise some questions about the mode of interpretation going on over this particular Sukta for over a long time. (Entire Sukta below in Griffith’s translation)
          The most ‘popular’ Rk is the 12^th one: “The Brahman was his mouth, of both his arms was the Raajanya made./ His thighs became the Vai?ya, from his feet the Shudra was produced.”
          Many scholars believe that the Caste-System evolved from this – and the Varnas stated as above actually point to a hierarchy – that is, since ‘mouth’ is at the top, Braahmana is at the top; since Shudra is born from the foot, then, Shudra must be at the lowest scale of Social Hierarchy. But for such logic to work, one has to assume that the Purusha is standing erect.
          What does the Rshi of the Sukta tell us? We find, he tells us that the Purusha is “sacrificed.” Then? How does the logic work that Braahmana is at the ‘top’ and Shudra is at the ‘bottom’? Yet, we find scholars forcing the logic.
          As an example, let us see what Irfan Habib writes about this:[1]
“When we actually come to the RgVeda’s own single statement about the Varnas in the Purusha Sukta (10.90) where the Braahmana, Raajanya, Vaishya, and Shudra are shown as springing from the various parts of the body of the sacrificed Purusha, it is clear that it is a simple declaration of social hierarchy, the class of priests, warriors, the masses, and the menials being placed in a descending order.”
         Habib notes: “it should be recalled that Vaishya in RgVeda seems to have the sense of a common man, derived from Viz, people. It is also noteworthy that the term Varna is not actually used in the passage. The passage is repeated in Atharva Veda 19.6, and Vaajasaneyi Samhitaa 31.11.”
        The Sukta is remembered in many other places; for example, in Mahabharata, it is also remembered with two minor variations regarding Vaishya; Vaishya is born from navel, and stomach. Besides, Mahabharata transforms Raajanya into Kshatriya.
My questions to Irfan Habib are humble and simple:

1. First of all, does the Rshi of RV- 10.90 say anything about the Purusha’s posture?
2. If the Purusha is “sacrificed,” (as Habib says), then is the Purusha standing or lying? If the Purusha is “sacrificed,” then the Purusha is obviously lying (horizontally, so to say), because once ‘sacrificed,’ how can Purusha still stand (be ‘vertical’)?
3. If the Purusha is lying, how is it “clear” to Habib “that it is a simple declaration of social hierarchy, the class of priests, warriors, the masses, and the menials being placed in a descending order?” Where does the question of “descending order” arise in lying posture? In fact, all the Four Varnas (Braahmana-Kshatriya-Vaishya-Shudra) come on the same plane - that is, the Rshi actually wanted to suggest equality of Varnas with different functions (if we at all take the Rk as speaking of Varna System)
4. Habib writes next: “Such a description could have been given of the society of any ancient or medieval civilization, and by itself hardly implies the existence of the caste system, though once the caste system was incorporated within the brahmanical code, this began to be cited as a narration of its original creation.” Question is: if Habib knows that Purusha Sukta “by itself hardly implies the existence of the caste system,” then how can Habib say just in the previous lines: “it is clear that it is a simple declaration of social hierarchy”? How does ‘clarity’ (“clear”) and “hardly” go together?

        Well, readers, let us ponder over the Strategies of Discourse-Construction! The learned scholars always keep Escape route open!
        My humble suggestion to readers is: let us not believe in what a scholar says; let us always read the original, and let us find out significances ourselves … firsthand.
        Let me also remind readers that in Mahaabhaarata Vyaasa’s father Paraashara says that Vishnu dwells in the foot, and in Braahmana texts we find, Praana enters the Body through foot – that is importance of foot is confirmed in our scriptures. We may also remember here that Krishna’s Praana exits ‘through his foot.’
        That would be a separate discussion.
        My point here is: the Orthodoxy that preaches on the basis of this Rk that Varna System is hierarchical, that this justifies ‘caste’ hierarchy, are as guilty as the scholars who preach that ‘caste’ and Varna are same, or that this Rk can be interpreted as hierarchy of Varnas.
 
Purusha Sukta (RV- 10.90) (Trans. Griffith)
1. A THOUSAND heads hath Purusha, a thousand eyes, a thousand feet.
 On every side pervading earth he fills a space ten fingers wide.
 2 This Purusha is all that yet hath been and all that is to be;
 The Lord of Immortality which waxes greater still by food.
 3 So mighty is his greatness; yea, greater than this is Purusha.
 All creatures are one-fourth of him, three-fourths eternal life in heaven.
 4 With three-fourths Purusha went up: one-fourth of him again was here.
 Thence he strode out to every side over what cats not and what cats.
 5 From him Viraaj was born; again Purusha from Viraaj was born.
 As soon as he was born he spread eastward and westward o’er the earth.
 6 When Gods prepared the sacrifice with Purusha as their offering,
 Its oil was spring, the holy gift was autumn; summer was the wood.
 7 They balmed as victim on the grass Purusha born in earliest time.
 With him the Deities and all Saadhyas and Rshis sacrificed.
 8 From that great general sacrifice the dripping fat was gathered up.
 He formed the creatures of-the air, and animals both wild and tame.
 9 From that great general sacrifice Rcas and Saama-hymns were born:
 Therefrom were spells and charms produced; the Yajus had its birth from it.
 10 From it were horses born, from it all cattle with two rows of teeth:
 From it were generated kine, from it the goats and sheep were born.
 11 When they divided Purusha how many portions did they make?
 What do they call his mouth, his arms? What do they call his thighs and feet?
 12 The Brahman was his mouth, of both his arms was the Raajanya made.
 His thighs became the Vai?ya, from his feet the Shudra was produced.
 13 The Moon was gendered from his mind, and from his eye the Sun had birth;
 Indra and Agni from his mouth were born, and Vaayu from his breath.
 14 Forth from his navel came mid-air the sky was fashioned from his head
 Earth from his feet, and from his car the regions. Thus they formed the worlds.
 15 Seven fencing-sticks had he, thrice seven layers of fuel were prepared,
 When the Gods, offering sacrifice, bound, as their victim, Purusha.
 16 Gods, sacrificing, sacrificed the victim these were the earliest holy ordinances.
 The Mighty Ones attained the height of heaven, there where the Saadhyas, Gods of old, are dwelling.