The community's antiquity is not the disputed part, and it is worth separating the two questions carefully because they are often argued as one. That Christians were long established on the Malabar Coast is beyond doubt: Cosmas Indicopleustes, writing in the sixth century, reported a church at a place he called Male with a bishop ordained in Persia, and the community's liturgy, canon law, script and hierarchy all came from the East Syriac Church of the East, a connection maintained for more than a thousand years until the Portuguese arrived and set about severing it.
What is disputed is whether the Apostle Thomas himself came. Leslie Brown's study of the community weighed the evidence at length and concluded that a first century mission to south India is possible, given the trade routes and the Jewish communities already present on the coast, but that it cannot be demonstrated from any source independent of the tradition itself.
A second position, held by historians who read the Malabar tradition as retrospective, treats the apostolic claim as a construction that gave an ancient but ordinary Persian-connected church a founding charter of its own. A third simply accepts it as the community's living memory and declines to submit it to the tests appropriate to a documented event. The atlas records the claim as the community holds it, marks it disputed, and names the camps, because to assert it would be to invent evidence and to omit it would be to silence a community about its own origin.