The Proto-Malayo-Polynesian language (PMP) is the reconstructed ancestor of the Malayo-Polynesian languages, which is by far the largest branch (by current speakers) of the Austronesian language family. Proto-Malayo-Polynesian is by definition ancestral to all (certain) Austronesian languages spoken outside Taiwan, and Yami language on Taiwan's Orchid Island. Tai–Kadai languages are hypothesized to be a branch of Austronesian (but not Malayo-Polynesian), further scientific investigation is necessary to determine the relationship. (see Austro-Tai languages). The first systematic reconstruction of Proto-Austronesian (="Uraustronesisch") by Otto Dempwolff was based on evidence from languages outside of Taiwan, and was therefore actually the first reconstruction of what nowadays is known as Proto-Malayo-Polynesian.
However, Roger Blench (2016) doubts that there was actually the existence of a single unitary Proto-Malayo-Polynesian language. Rather, Malayo-Polynesian expansion across the Luzon Strait consisted of multi-ethnic crews rapidly settling across various locations in maritime Southeast Asia, as suggested by both archaeological and linguistic evidence. There was also a Malayo-Polynesian migration to Hainan; Blench (2016) notes that both Hlai and Austronesian peoples use the foot-braced backstrap loom as well.