The internal classification of Mixtec is controversial. Many varieties are mutually unintelligible and by that criterion separate languages. In the 16th century, Spanish authorities recognized half a dozen lenguas comprising the Mixtec lengua. (See #Classical Mixtec.) It is not clear to what extent these were distinct languages at the time. Regardless, the colonial disintegration of the Mixtec nation and resulting isolation of local communities led to the rapid diversification of local dialects into distinct languages. Below are some attempts at Mixtec classification by various scholars.