In the complex issue of dating the Caṅgam corpus, one can take into account several factors:
- 1. metrum: The eldest hymns are composed in a certain metrum. Added stanzas, mostly invocation ones, are in another metrum.
- 2. "anthologization marks": At a certain points, redactors started to create an anthology of this kind of literature and tried, thus, to make works look uniform. One of these marks is the addition of an invocation stanza (akin to the Sanskrit maṅgala) at the beginning.
- 3. Deities: It seems that in the most ancient Dravidian history (and, hence, in the corresponding layer of the Caṅgam corpus), deities were conceived in a specific way, i.e., they had neither name nor form, they were linked to a specific place and were always in a group [one is reminded of spiriti loci, possibly akin to Japanese deities]. Next, their implements (weapons, the flute…) start playing a role. This is possibly linked to the fact that such implements played a role in the ritual reactualization of their worship. As a third step, a concept of a precise deity is elaborated. Last, a personal, iconic worship finds its way in the texts.
On the workshop on Viṣṇu-Nārāyana, see this post.