Penelitian ini menjelaskan perubahan dan pewarisan bunyi vokal PAN ke dalam bahasa Angkola (BA) dan bahasa Simalungun (BS). Linguistik Historis Komparatif(LHK) adalah pendekatan yang digunakan dalam penelitian ini. Data yang digunakan ialah 200 daftar kosakata swadesh dan pengumpulan data tulis ialah dengan metode simak yang dilanjutkan dengan teknik sadap. Pengkajian data menggunakan metode perbandingan historis. Penyajian hasil analisis akan dilakukan dengan cara penyajian formal. Berdasarkan analisis ditemukan pewarisan linear (retensi) dalam bahasa Angkola */a/ → /a/, */i/→ /i/, */u/ → /u/, dan pewarisan fonem vokal PAN secara inovasi */a/ → /E/, */ ə / → /o/. Pewarisan proto austronesia pada bahasa Simalungun secara linear */a/ → /a/, */i/→ /i/, dan pewarisan fonem vokal PAN secara inovasi */ ə / → /o/.
This research discusses the changes and inheritance of the PAN vowels into Angkola (BA) and Simalungun (BS) languages. This research was conducted using a comparative historical linguistic approach. The data used were 200 swadesh vocabulary and the method collected in collecting written data was the observation method followed by the tapping technique. The study of data used the historical comparison method. Presentation of the results of the analysis will be carried out by means of a formal presentation. Based on the analysis, it was found that linear inheritance (retention) in Angkola language * / a / → / a /, * / i / → / i /, * / u / → / u /, and innovation of the PAN vowel phoneme * / a / → / E /, * / ə / → / o /. The inheritance of the proto austronesian in the Simalungun is linear * / a / → / a /, * / i / → / i /, and the innovative inheritance of the vowel phoneme PAN * / ə / → / o /.