According to Robert Blust, the Formosan languages form nine of the ten primary branches of the Austronesian language family (). noted this when he wrote: ... the internal diversity among the... Formosan languages... is greater than that in all the rest of Austronesian put together, so there is a major genetic split within Austronesian between Formosan and the rest... Indeed, the genetic diversity within Formosan is so great that it may well consist of several primary branches of the overall Austronesian family.At least since , writing in 1949, linguists have generally accepted that the chronology of the dispersal of languages within a given language family can be traced from the area of greatest linguistic variety to that of the least. For example, English in North America has large numbers of speakers, but relatively low dialectal diversity, while English in Great Britain has much higher diversity; such low linguistic variety by Sapir's thesis suggests a more recent origin of English in North America. While some scholars suspect that the number of principal branches among the Formosan languages may be somewhat less than Blust's estimate of nine (e.g. ), there is little contention among linguists with this analysis and the resulting view of the origin and direction of the migration. For a recent dissenting analysis, see .