around 950 by Constantine Porphyrogenitus in his De Arte Imperiando, "the inhabitants of the district of Maina... are of the older Greeks, who are to this day called Hellenes (pagans) by the locals for being pagans in time past and worshippers of idols, like the Hellenes of old, and were baptised and became Christians during the reign of the late Basil (867–886)", with Maina in his usage typically interpreted to instead mean Tsakonia. The Tsakonians are thought to have been often border guards in the Byzantine military, judging by the number of references to τζάκωνες and τζέκωνες playing such roles in Byzantine Greek writings. The first reference to their "barbaric" speech being unintelligible to Koine Greek dates to the 15th century. According to the Byzantine historian George Pachymeres, some Tsakonians were resettled by the Byzantine emperor Michael VII Ducas in Propontis. This was part of their compensation for serving as marines in the Byzantine Navy. They and the Peloponnesian Gasmouloi, who served in the same role, were dismissed from service by Michael's successor, Andronicus II, who made large reductions in the naval force, preferring to rely on Genoese mercenaries. They lived in the villages of Vatka and Havoutsi, where the Gösen River (Aesepus) empties into the sea. However, based on the preservation of features common to both Propontis and the Peloponnesian dialects, Prof. Thanasis Costakis thinks that the date of settlement must have been several centuries later. Population The Tsakonians ( Tsákones) are a Greek ethnolinguistic group who historically speak the Tsakonian language and have certain peculiar cultural traditions, such as the Tsakonian dance. Today, the language is critically endangered. Tsakonians in later time were known for their masonry skills; many were also shepherds. A common practice was for a small crew of men under a mastora to leave their village after the feast of Saint Demetrius and to return at Easter. They would travel as far as Attica doing repairs and white-washing houses. The Tsakonian village of Kastanitsa was known for its chestnuts and derives its name from the Greek word for the nut. Genetic studies The paper "Genetics of the peloponnesean populations and the theory of extinction of the medieval peloponnesean Greeks" (2017) studied the Tsakonians under two groups; one from the South (15 samples) and one from the North (9 samples) of the region. Both populations have a very high average pairwise IBD sharing of 0.66% of