This section is from the book "Some Contributions Of South India To Indian Culture", by S. Krishnaswami Aiyangar. Also available from Amazon: Some Contributions of South India to Indian Culture.
Tamil tradition of comparatively late age describes the Tamil country as mainly composed of forests and practically uninhabited till Agastya came from the far north. In a solemn conclave on the Himalayas the Devas and the Rishis had assembled on one occasion. Finding the earth sinking from the weight of the august assembly and much exercised about this phenomenon, they hit upon the device of sending somebody to the south to balance the assembled weight of the north, and pitched upon Agastya, who alone of all those assembled was capable of balancing the rest of them all together. When the request was made to him he readily agreed to proceed on such a great errand of benefit to this divine humanity. Starting southwards therefore on this beneficent mission Agastya went first to the Ganges and obtained from her the river Kaveri. Then he went to the Rishi Jamadagni and took from him his son Trnadhumagni, and from Rishi Pulastya his virgin sister Lopamudra. Going further onward in his journey he came to Dvaraka, and took from there 18 of the ruling family of Vishnu (Vrsnis), and 18 crores of two classes of people Velir and Aruva]ar. With such a following he proceeded south destroying the forests, and transforming the forest-region into inhabited country till he made his home in the hill of Podiyil in the southern part of the Western Ghats keeping Havana and his Rak-shasas away from that part of the country. It was then that he ordered his disciple, the son of Jamadagni to go and fetch his wife, keeping a distance of four rods' length on all sides of her in the course of their journey. As they were crossing the river Vaigai a sudden flood carried her off. Going forward to her assistance, and, putting forward a bamboo stick for her to take hold of, the dutiful pupil brought her successfully out of the water, and then took her to his master. For this transgression of instructions Agastya pronounced both of them ineligible for entry into heaven. Protesting their innocence they in turn said that he might have a similar fate also for his inconsiderate anger. It was on account of this anger of the master that he directed his disciple's grammar Tolkappiyam, as the disciple assumed the name Tolkappiyar, since his advent into the Tamil country, be not heard. The point in this story is that the reclamation of the forest tracts in this region is somehow associated with a southern migration led by Agastya, and among the tribes that came with him are found mentioned Velir and Aruvalar, two well-known peoples of Tamil India. For this Tamil land the most accepted boundary given is the Tirupati hill in the north (Vidavengadam), Cape Comorin (Kanyakumari) in the south, and the two seas on either side. Whenever this great migration took place, and whether such a migration was historical or no, there is something like the march of civilisation from the north into the south, and under northern guidance and influence. Agastya himself came and brought a disciple along with him, the son of another sage. Along with him came presumably the northern culture especially associated with the Brahman.
Leaving tradition aside we have evidence, in the earliest extant literature of the Tamil land, of the very high position ascribed to the Brahman in the literature of the south. In one of the earliest of the Tamil classics recently made available a king is described as following the path of the "Andanar" (Brahmans) who follow the Dharma by doing the six duties imposed upon them by immemorial prescription. These are described as learning and teaching, sacrificing and conducting sacrifices, receiving gifts made to them and making gifts to others.1 In the same collection comes later on a reference to another monarch of the same dynasty where he is spoken of as "not knowing obedience except to Brahmans." The authors in these two cases happen to be themselves Brahmans. In the one, the author was a Brahman by name Gautama who was distinguished for composing poems in a particular mode in Tamil. He celebrated the father of Sem-Kuttuvan and requested as a favour that he and his Brahman wife should go to heaven. This Chera consulted other elderly Brahmans how this could be done to Gautama. Under their advice he celebrated ten Vedic sacrifices on the completion of the tenth of which the Brahman and his wife ceased to be visible. The other one is the famous poet by name Kapilar. This Brahman was regarded as a model of a virtuous man and spoken of in such terms by poets who were not themselves Brahmans. He celebrates another Chera by name Selvak-Kadungo. The same description of the ordinary occupation of the Brahman is given in the classical grammar Tolkappiyam where the Grammarian lays down what were the customary occupations of the Brahmans. The same six occupations are there given as those to which they generally devoted themselves.2 Almost the same language is used in referring to the Brahman by Buddhist and Jain writers in similar connections. The Silappadhikaram, a work of the Chera prince-ascetic Ilango, refers to what happened to Gautama above referred to in the account that is given of a Brahman Parasara of the Chola country who went on a visit to the Chera "who gave heaven itself to the Brahman Gautama," having heard of his great liberality. In describing this Brahman this author1 speaks of him as one devoted to the attainment of heaven, of two births, whose wealth consisted in the three fires, whose learning embraced the four Vedas, who had special charge of the celebration of the five sacrifices and whose chief occupation consisted of the six items: learning and teaching, sacrificing and conducting sacrifices for others, receiving in gift and giving, brought in under the same epic category as the grammatical enumeration referred to in Tolkappiyam above "of the victorious Brahman" (parppana-vakai). Strangely enough on his return journey he came to a Buddha Vihara2 at a Brahman village Tangal in the Pandya country and halted there in the course of his journey. In the companion work Manimekhalai3 also we come upon references almost exactly the same in tenor to the occupation of the Brahman although that work, true to its character, in one connection1 holds up to ridicule the celebration of these sacrifices by inflicting pain upon the animals sacrificed. It will thus be seen that although these references are found in the literature of the first centuries of the Christian era they indicate an immigration of the Brahman in times much anterior, and the character of the Brahmanism of which we gain glimpses in this literature shows itself to be pre-Buddhistic.