Though Vaishnavites are primarily monotheistic in their philosophy, they do not demand exclusivity. Vaishnavites usually don a unique 'V' shaped mark in the middle on their forehead and sometimes on their forearms. The mark is etched in white with a vertical red or yellow stroke. The marks on the forehead signify the feet of Vishnu, which designates absolute submission. Variations in this mark discriminates northern sects from southern sects of Vaishnavites. With such inspiring and stimulating principles, Vaishnavism however shared its origin with various theories besides being just espousers of Lord Vishnu. There survives no comprehensible evidence about the origin of Vaishnavism in India, but its development from the medieval period had been quick and incredible.
Though some form of worship existed during the pre-Christian era, origin of Vaishnavism and its germination into an established religion, happened only during the post-Christian era. Doctrine of Trinity, Doctrine of Avatar and the Doctrine of Fulfillment of Sacrifice are the fundamental doctrinal aspects of Vaishnavism. The literal origin of Vaishnavism is believed to have sprouted from Early Indian Christianity. Early Indian Christianity was of the habit to observe the umpteen elements and facets of Dravidian worships that prevailed during the pre-Christian era and developed eventually as Vaishnavism. With time, this separatist faction of Hinduism had begun to spread its wings to further lands, precisely in remote parts of the country. Vaishnavism hence evolved as a Bhakti movement approximately during 6th and 7th century A.D. in South India and further disseminated towards the North. However, the total camouflaged aspect of the Brahman concept under the name of Hinduism, generally led to the widespread belief that the Vedas are the basis for the development of this Bhakti Movement. By and large, Vaishnavite Vishnu is identified with Vedic Vishnu. A thoroughgoing study of the Vedas will unveil the secreted truths that Vaishnavism has nothing to do with the Vedic Rudra or Vishnu.
Origin of Vaishnavism in India owes much also to the Sanskritic ages, during the period of the epics. The monotheistic reverence of Vishnu was already well developed in the period of the Itihasas (literally meaning "so it happened", Itihasas refer to the epic poetry penned in India and originally scripted in Sanskrit). Vaishnavism is elaborated and exposited in that cardinal section of the Mahabharata known as Bhagavad Gita, which assimilates the words of Shri Krishna, one of the avatars of Vishnu. Many of the ancient rulers, beginning with Chandragupta II (hugely popular as Vikramaditya) were identified as Parama Bhagavatas, or Bhagavata Vaishnavas. Vaishnavism had also witnessed steeping rise of flourishing in South India during the seventh to tenth centuries CE. The fact that the religious faction is still absolutely espoused, especially in Tamil Nadu, owes much to the twelve Alvars, saints who had distributed Vaishnavism to the common people with their devotional hymns. The temples which the Alvars used to pay visits or founded are presently known as Divya Desams. Their poems in extolment and eulogising of Vishnu and Krishna in Tamil language are collectively recognised as Naalayira (Divya Prabandha). In comparatively later centuries, Vaishnava practices improved in popularity due to the tremendous influence of sages like Ramanujacharya, Madhvacharya, Manavala Mamunigal, Vedanta Desika, Surdas, Tulsidas, Tyagaraja and several others.
Vedic Origin of Vaishnavism
Although Vedic Age is not attributed with the successful origin of Vaishnavism in India, yet it cannot be denied that the Vedas and its time-period had impressed upon the Vaishnavites profoundly. Lord Vishnu is one of the Gods which were worshipped by the Vedic Aryans. He was not one of the more authoritative ones, yet he outlasted all his Vedic rivals to reign supreme amongst the Aryan Religion. This was possible because of his features of incarnation. Most other Vedic gods like Indra or Brahma, were adjudged as incarnations of Vishnu, as were several other minor non-Vedic Aryan tribal deities, like the deified king Rama and Krishna. In the same way, many local pre-Brahmanic gods were adjudged as incarnations of Vishnu, leading to the incredible circularisation of Vaishnava religion. Soon, the original Vedic religion was divided into two faiths: Vedism and Vaishnavism. Pockets of pure Aryan Vaidiks, who declined to adopt the Puranas and other Vaishnava scriptures, remained. Vaishnavism and Vedism are however still classed under the term of 'Brahmanism'. Two pre-Aryan gods although could not be integrated into this Vaishnava pantheon, consisting of Lord Shiva (the Dravidian God) and Mahadev (the Tibetic God of Tantrism).
As Vedism worsened down, the Vaishnavism cult egressed potently and revolved around Vasudeva, the exalted Vrsni hero. Origin of Vaishnavism again comes face to face with contrasting visions; there exists evidence that worship of Vasudeva and not Vishnu had arrived at the offset of Vaishnavism. This earliest chapter was established from the sixth to fifth centuries BCE, during the domination of Panini, who in his Astadhyayi had delineated the word 'vasudevaka' as a bhakta, devotee of Vasudeva. Another cult that flourished with the declination of Vedism was pivoted around Krishna, the exalted tribal idol and religious leader of the Yadavas. The Vrsnis and Yadavas came nearer to each other, leading to the unification of Vasudeva and Krishna. This occurrence had initiated early as the fourth century BCE, according to evidence in Megasthenes and in the Arthasastra of Kautilya (also admired as Chanakya).
North India had also witnessed significant origin of Vaishnavism through its umpteen Vaishnava movements under venerated luminaries, like: Nimbarka in the fourteenth century with the cult of Radha; Ramananda and the cult of Rama in the same century; Kabir during the fifteenth century, whose Lord was Rama; Vallabha in the sixteenth century with the worship of the boy Krishna and Radha; and Chaitanya in the same century with his worship of the adult Krishna and Radha. In the Maratha territories poet-saints like Namdev and Tukaram from the fourteenth to the seventeenth centuries had also worshipped Vishnu in the form of Vithoba of Pandharpur.