"We need not agree with the Śāstrakāra-s that the varnāśramadharma is truly “Vedic”, for we do not find it in the first nine books of the Rg-Veda. Even in the tenth book, the last and youngest one, we find it mentioned only once, and there only in the vaguest use, viz. the Purusa Sūkta’s recognition of the existence of four functions in society, without any details of how their personnel is recruited nor of how they should conduct themselves vis-à-vis one another, the very stuff that is the main focus of the Śāstra-s. Like medieval and contemporary Hindus, the Śāstra composers may have considered as ”Vedic” everything they held sacred, regardless of whether a particular norm or custom is indeed traceable to the Veda-s."
January 1, 1970
https://en.wikiquote.org/wiki/Purusha_Sukta