Does scripture explain how the castes became different after birth from Purusha?

Question

The authoritative Rig Veda says in the Purusha Sukta

ब्राह्मणो''ऽस्य मुख'मासीत् | बाहू रा'जन्यः' कृतः | ऊरू तद'स्य यद्वैश्यः' | पद्भ्याग्^म् शूद्रो अ'जायतः ||

The ‘brāhmaṇa’ was his mouth, the ‘kṣatriya’ was made of His two arms, then His two thighs became the ‘vaiśya’, from His feet the ‘śūdra’ was born. (12)

This means that the four castes started exactly the same way - ayonija birth from the same Purusha, or Cosmic Man.

Modern Genetics says one's genes are the same throughout the body with some small exceptions. At least according to modern genetics, the four castes were genetically largely identical in the beginning.

Does scripture say how they became differentiated after their birth from Purusha?

Answer 1

Varnas were not separated from creation. They later separated by the Karma of people.

Bhrigu said, 'There is really no distinction between the different orders. The whole world at first consisted of Brahmanas. Created (equal) by Brahman, men have, in consequence of their acts, become distributed into different orders. They that became fond of indulging in desire and enjoying pleasures, possessed of the attributes of severity and wrath, endued with courage, and unmindful of the duties of piety and worship,--these Brahmanas possessing the attribute of Passion,--became Kshatriyas. Those Brahmanas again who, without attending to the duties laid down for them, became possessed of both the attributes of Goodness and Passion, and took to the professions of cattle-rearing and agriculture, became Vaisyas. Those Brahmanas again that became fond of untruth and injuring other creatures, possessed of cupidity,--engaged in all kinds of acts for a living, and fallen away from purity of behaviour, and thus wedded to the attribute of Darkness, became Sudras. Separated by these occupations, Brahmanas, falling away from their own order, became members of the other three orders.

Moksha Dharma Parva

Answer 2

Rg Veda 10.90.12 is mostly misrepresented in colonial translations as the source of the scriptural authority for the "caste system", because the analogy for Purusha is a "man, standing", hence the hierarchy. But what really does the verse say?

Here is the colonial translation:

At the top of the hierarchy were the Brahmins who were mainly teachers and intellectuals and are believed to have come from Brahma's head. Then came the Kshatriyas, or the warriors and rulers, supposedly from his arms. The third slot went to the Vaishyas, or the traders, who were created from his thighs. At the bottom of the heap were the Shudras, who came from Brahma's feet and did all the menial jobs.

And here is the real meaning, as paraphrased:

From this cosmic intelligence, we derive the four most desirable traits of character, namely wisdom, nobility, industry, and talent or facility.

Purusha (energy) and Prakriti (matter) represent the duality of all creation. Purusha in the Rg Veda is not standing man. Just as the constellation of Orion is visualized as the Nataraja, Purusha here represents the sum total of energy in the universe, Prakriti the sum total of matter in the universe. So any representation in the analogy is not associated with a hierarchy, nor does Purusha represent humans alone. Purusha & Prakriti together represent the sum total of the duality of all creation. Further, a verse from the Skanda Purana [SP 18.VI.239] asserts "janme jayate shudra...", meaning all humans are born with some talent or facility. That, if you wish to go into "public service" to serve the people of the land, then you must train long and hard to qualify to be a dwija! Thus, one could say, that Shudra is just another word for the "talented citizens" of a kingdom or country, essentially 90% of all citizens.

Make what you want of this!

UPDATE: Since some of you asked, "caste" (Portuguese for "race"), has no authority in the Veda. In fact, there is no word that is equivalent to "caste" in any Indian language - Sanskrit or any of the Prakrits.