Karo as a decent language has a historically genetic similarity to its ancestral Proto-Austronesia (PAN). It inherits a number of PAN’s lexicons but, after splitting from its mother tongue, evolutionally it evolves and even deviates in its own way according to its environment. Its inheritance system is linear and even innovative. The innovative inheritance usually occurs in the inheritance of the vowels rather than the consonants. Therefore, this paper aims to analyze the inheritance of PAN’s vocals in Karo. The analytical data uses 200 Swadesh's list of vocabulary on the grounds that the basic vocabulary tends to be constant/difficult to change. The theory of historical comparisons was used. From the analysis it is concluded that the vowel phoneme *ǝ was inherited linearly, while the vowels *a, *i, and *u> are innovatively inherited, i.e. *a> a, ǝ, ​​and e; *i> i and a; *u> u, o, i, and ǝ. All this means the vowels *u, a, and ǝ have merged > ǝ; *i and *u have also merged > a; *u, *a, and ǝ have undergone both partial splits and mergers> u, a, and ǝ in Karo.