The hymn "Purusha Sukta" to the "Rigveda" describes the symbolic creation of the four varna-s through cosmic sacrifice (yajña). Some scholars consider the "Purusha Sukta" to be a late interpolation into the "Rigveda" based on the neological character of the composition, as compared to the more archaic style of the Vedic literature. Since not all Indians were fully regulated under the varna in the Vedic society, the "Purusha Sukta" was supposedly composed in order to secure Vedic sanction for the heredity caste scheme. An alternate explanation is that the word 'Shudra' does not occur anywhere else in the "Rig-veda" except the "Purusha Sukta", leading some scholars to believe the "Purusha Sukta" was a composition of the later Rig-vedic period itself to denote, legitimize and sanctify an oppressive and exploitative class structure that had already come into existence.