The early evolution of the shaiva fold is a topic of tremendous interest (I am only grazing the surface with regards to a few points here. One may see some other notes on this topic elsewhere on this site). We obviously have no strong traces of its para-vedic elements. But there are several texts that pertain to the branching point of shaiva from within the old vedic tradition. These texts include chiefly the rudra pa~nchavaktra mantra-s and the shvetAshvatara of the kR^iShNa yajurvedic tradition and the atharvashiras and the nIlarudra of the atharvavedic tradition. Many principal elements of the shvetAshvatara and the nIlarudra derive from the vedic rudra sUktaM-s seen in the R^ig, yajur and atharvan saMhitAs. In the mahAbhArata we already have sections that are clearly of a generalized shaiva origin and express their clear connection to the vedic tradition including the importance of the shatarudriya hymns borrowed from the classical vedic ritual tradition. In addition, they provide an important hymn resembling the shatarudriya in many ways, which is the ajAnana virachita rudra stuti. The paurANic, classical and inscriptional evidence one can discern that the shaiva fold had already differentiated into multiple distinct streams.
While the naming system of these streams is varied and sometimes confused the following can be made out:
1) pAshupata (this name is almost an invariant). 2) kApAlika (this stream may be called the saumya or somasiddhAntin-s after their connection with the soma sacrifice. They may in some accounts also be be called mahAvrata-dhara). 3) The lAkula after their founder lAkula or lAkulIsha (this name is often misspelt in different sources, and may often be known by their later name kAlAmukha-s). Some source may also call them mahAvrata-dhara). 4) The tantric shaiva-s. This group originally further diversified to 5 lineages or srotas with their texts being: the bhUta, vAma, bhairava, garuDa and siddhAnta tantras. The originally shAkta tantric lineage, the trika tantras or the siddhayogeshvarI-mata shaivized (most likely in the Tamil country and spread to Kashmir where it underwent an efflorescence) and added to the tantric shaiva stream. The popular bhakti stream of shaiva was closely linked to the lAkulIsha stream and appears to have been a public ofshoot for the general populace supported by the lAkula AchAryas. To a lesser extant it incorporated the pAshupata-s too. The “Elephanta” caves built by the kalachuri king kR^iShNa rAja (around mid 500 AD) and the closely linked finalized shiva purANa are closely linked to the lAkulIsha shaivas. dakSiNa-kedAreshvara in Karnataka is another major temple built under the instigation of the later lAkula-s, the kAlAmukha-s. The lAkula-s were a pan-India phenomenon. Seen in many spots in south India down to the Tamil country, in somanAtha in Gujarat, Mathura (both major centers) and Kashmir.
The lAkula-s were clearly related to the pAshupata-s and may have shared a common ancestral development and then diverged. Their ancestor seems to be a very early shaiva branch with clear links to the vedic texts. The pAshupata sUtra itself is attributed to the founder of lAkula-s, lAkulIsha. lAkulIsha’s disciple musalendra wrote a work termed hR^idyapramANa of which only fragments survive in a later lAkula commentary. Another successor of lAkulIsha, a kauNDinya composed the pa~nchArtha bhAShya of the pAshupata sUtras. These works seem to be chiefly the texts of the lAkula-s and later kAlAmukhas and are principally highly ascetic in nature. The common follower is merely asked to perform japa of the pa~nchAkShari. The lAkula ascetic may follow many strange ways. He may if he wishes wander entirely naked or with just a kaupIna. He has ash baths and performs penances. He meditates in rudra shrines and may perform aTTahAsa or sing and dance loudly showing lewd gestures. He sleeps on ashes and worships the lAkulaugha AchAryas starting with lAkulIsha when bathing. He utters huDukAra 3 times before uttering the pa~nchAkShari. He shuns women entirely and observes strict celibacy. The path is only for dvijas. If he touches a woman he must purify himself with prANAyAmas and the rudra gAyatrI. They also may perform praNava japa to gain greater asceticism. Thus, the lAkula shaiva is different from the classical tantric shaiva-s in that he observes entirely orthodox vedic elements and strict celibacy despite the outward facade of “contrary behavior”.
The classical pAshupatas in contrast seem to derive directly from none other shvetAshvatara and we get information about their early history chiefly from the analysis of the most ancient version of the pAshupata vrata provided in the parishiShTa 40 of the atharvan literature. Their links to the atharva tradition is also established by the use of a particular rudra mantra that is unique to Atharvavedins (though not recorded in any extant saMhitA):
rudraM kruddhAshanimukhaM devAnAM IshvaraM paraM |
shveta-pi~NgalaM devesham prapadye sharaNAgataH ||
yasya yuktA rathe siMhA vyAghrAsh cha viShamAnanAH |
tam ahaM pauNDarIkAkShaM devaM AvAhaye shivaM ||
The pAshupata-s also deploy the atharvedic dvaya rudra formulae for the ghee offerings.