 Modern linguistics is not in accord with the tendency of the 19th century scholars to regard modern Greek dialects as the direct descendants of the dialects of ancient Greek.According to the latest findings of scholarship, modern Greek dialects are products of the dialect differentiation of Koine Greek, and, with the exception of Tsakonian, they have no correlation with the ancient dialects.It is difficult to monitor the evolution of Koine Greek and its splitting into the modern Greek dialects; certain researchers make the hypothesis that the various local varieties were formed between the 10th and the 12th century (as part of an evolution starting a few centuries before), but it is difficult to draw some safer conclusions because of the absence of texts written in the vernacular language, when this initial dialect differentiation occurred.