According to Schopen, there are no "earliest" records. As you know, he basically does not think anything is reliably datable based on text criticism alone.
That doesn't undermine what I'm saying. Our earliest specimens of Buddhist literature are translations of other materials (even the Pali), yet even if they're from around the first century CE onward they don't mention writing as being part of society or religion in Magadha. As far as I know, nor do Jain texts make such references.
Megasthenes had very limited contact with Indian culture and civilization.
He did live there for some time. Your argument is silly.
We can say with certainty that Ashoka used writing. We cannot say with certainty when writing first was used in India and by whom. All we can really say with certainty is that it, like most other scripts in the ancient world, was based on Western Semitic, where aleph = an Ox.
You're saying "it is quite likely that some form of writing existed in India during the time of Buddha." Well, you have no evidence for this.
I'm quite solid in my position stating that later developments in Vinaya literature where the Buddha is talking about drawing up loan contracts with people is in fact a much later development and moreover an indication of ignorance on the part of the author(s), who were unaware that writing didn't exist in the Buddha's day. As a Buddhist, I don't feel much faith towards their ideas in this respect. It isn't buddhavacana
, but really just opportunism of a sick kind. So, what amount of Vinaya literature, prescriptions and proscriptions are we supposed to take seriously?
I personally think just following the basic outline of a śramaṇa lifestyle is enough. However, this undermines the authority of some ecclesiastical authorities, so predictably not much will ever change.
Nevertheless, there's still the option of being outside the authority of such institutions.