"An organised Christian presence in India dates to the arrival of East Syriac settlers and missionaries from Persia, members of what would become the Church of the East, in around the 3rd century. Saint Thomas Christians trace the further growth of their community to the arrival of Christians from the Middle East led by Knāy Thoma (anglicized as Thomas of Cana) , which is said to have occurred either in the 4th or 8th century.  The subgroup of the Saint Thomas Christians known as the Knanaya or Southists trace their lineage to Thomas of Cana, while the group known as the Northists claim descent from the early Christians evangelized by Thomas the Apostle." - Wikipedia St Thomas Christians
The J-M241 project has four men in the otherwise mostly European L283 branch who trace descent to Syrian Christians of India, also known as St Thomas Christians. They form a cluster of men with absolute genetic distance of 8-12 at 67 markers (equivalent to FTDNA's genetic distance of 5-8). Their common ancestor may have lived around 1000 years ago, roughly estimated on the basis of STRs.
Their closest relatives are fully formed FGC64029 descending from a man who lived around 70 AD in the Levant. One of the Syrian Christians is positive for Y146401 • BY46462 and negative for the remaining J-FGC64029 SNPs. So the common ancestor of the Syrian Christians of India and the Lebanese FGC64029 lived around 1200 BC.While FGC64029 was most likely living in the Levant around 70 AD, his next closest relatives in the project are Albanian and French (predicted) and their common ancestor lived 1200 BC. We think their L283 ancestors were living in Europe (maybe originally having come from the N Caucasus) based on ancient L283 samples in Croatia and N Caucasus and the greater diversity in Europe rather than other regions.
Since the Levant also seems like a reasonable place from which Syrian Christians may have migrated to India, the simplest explanation is that the common ancestor of J-Y146401 • BY46462 lived in the Levant in 1200 BC. Because the next distant branching point is about the same time and not found in Asia, it is likely that the migration to the Levant took place 1200 BC.
Many theories are viable given this time frame and direction, which corresponds with the Bronze Age Collapse of Mediterranean civilizations. Interestingly, one of the FGC64029 is from Fidar, Lebanon which is only three km away from Byblos, an important city that was destroyed by the Sea People in 1200 BC. Prior to its destruction, control of Byblos had passed from Hyksos to Egyptian hands.
There are many theories about who the Sea Peoples were, and an Aegean origin is one of them. So perhaps the ancestor of J-Y146401 • BY46462 came from the Aegean or elsewhere in Europe as one of the Sea Peoples which sacked Byblos.
With only one NGS sample from the Saint Thomas Christians of India it is not yet possible to accurately calculate when their most recent common ancestor lived. However, based on the STRs it looks like the migration to India may have occurred anytime between 70 AD and the 11th century, when the most recent common ancestor of this exclusively Indian cluster may have lived.
Despite one of the surnames of these four living Syrian Christians of India being one which, according to oral history, represents a family of Brahmins who were converted by Saint Thomas, the true genetic origin of this man's male lineage is certainly the Levant.
If living descendants are found somewhere along the path between the Levant and India, we may someday get a better idea of the trajectory that these men's ancestors followed.
This finding suggests genetic continuity of Syriac Rite Christian practice in India for at least 1000 years.
This is one of the most interesting results I have yet found through genetic genealogy.