Proto-Austronesian

The Proto-Austronesian language (PAN) is the reconstructed ancestor of the Austronesian languages, one of the world's major language families. However, Ross (2009) notes that what may be the most divergent languages, Tsou, Rukai, and Puyuma, are not addressed by the reconstructions, which therefore cannot claim to be the protolanguage of the entire family. He calls the unit which has been reconstructed Nuclear Austronesian. Lower-level reconstructions have also been made, and include Proto-Malayo-Polynesian, Proto-Oceanic, and Proto-Polynesian. Recently, linguists such as Malcolm Ross and Andrew Pawley have built large lexicons for Proto-Oceanic and Proto-Polynesian.

Proto-Austronesian is reconstructed by constructing sets of correspondences among consonants in the various Austronesian languages, according to the comparative method. Although in theory the result should be unambiguous, in practice given the large number of languages there are numerous disagreements, with various scholars differing significantly on the number and nature of the phonemes in Proto-Austronesian. In the past, some disagreements concerned whether certain correspondence sets were real or represent sporadic developments in particular languages. For the currently remaining disagreements, however, scholars generally accept the validity of the correspondence sets but disagree on the extent to which the distinctions in these sets can be projected back to proto-Austronesian or represent innovations in particular sets of daughter languages.

Below are Proto-Austronesian phonemes reconstructed by Robert Blust, a professor of linguistics at the University of Hawaii at Manoa. A total of 25 Proto-Austronesian consonants, 4 vowels, and 4 diphthongs were reconstructed. However, Blust acknowledges that some of the reconstructed consonants are still controversial and debated.

...
Wikipedia