The Brahmin was his mouth, of both his arms was the (Kshatriya) made. His thighs became the Vaishya, from his feet the Sudhra was produced. (X.90.1-3)
This verses clearly points out that caste is innate and hereditary, that Jati depends on which part of Purusha humans came from and cannot be changed (except through rebirth).
The Shrutis lay the foundation of the caste system and the Smritis go on to sanction it in its ugliest form.
You don't know Shambhu Ji?
Sharam karo, ek apavitr aur ashuddh moorakh tumhen tumhara dharam sikha raha hai... Ram, Ram, Ram.
Heh! ;)