The Ancient South Arabian script branched from the Proto-Sinaitic script in about the late 2nd millennium BCE. It was used for writing the Old South Arabian languages Sabaic, Qatabanic, Hadramautic, Minaean, and Hasaitic, and the ancient language of Eritrea, Geʽez in Dʿmt. The earliest instances of the Ancient South Arabian script are painted pottery sherds from Raybun in Hadhramaut in Yemen, which are dated to the late 2nd millennium BCE. There are no letters for vowels, which are marked by matres lectionis.

The Proto-Sinaitic script is a Middle Bronze Age writing system known from a small corpus of about 30-40 inscriptions and fragments from Serabit el-Khadim in the Sinai Peninsula, as well as two inscriptions from Wadi el-Hol in Middle Egypt. Together with about 20 known Proto-Canaanite inscriptions, it is also known as Early Alphabetic, i.e. the earliest trace of alphabetic writing and the common ancestor of both the Ancient South Arabian script and the Phoenician alphabet, which led to many modern alphabets including the Greek alphabet. According to common theory, Canaanites or Hyksos who spoke a Canaanite language repurposed Egyptian hieroglyphs to construct a different script.