Proto-Sinaitic (also referred to as Proto-Canaanite when found in Canaan, or Early Alphabetic) is found in a small corpus of 40 inscriptions and fragments, the vast majority from Serabit el-Khadim in the Sinai Peninsula, dating to the Middle Bronze Age. They are considered 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 Semitic language repurposed Egyptian hieroglyphs to construct a different script.
The earliest Proto-Sinaitic inscriptions are mostly dated to between the mid-19th (early date) and the mid-16th (late date) century BC.
The principal debate is between an early date, around 1850 BC, and a late date, around 1550 BC. The choice of one or the other date decides whether it is proto-Sinaitic or proto-Canaanite, and by extension locates the invention of the alphabet in Egypt or Canaan respectively.
However, the discovery of the two Wadi el-Hol inscriptions near the Nile River suggests that the script originated in Egypt. The evolution of Proto-Sinaitic and the small number of Proto-Canaanite inscriptions from the Bronze Age is based on rather scant epigraphic evidence; it is only with the Bronze Age collapse and the rise of new Semitic kingdoms in the Levant that Proto-Canaanite is clearly attested (Byblos inscriptions 10th–8th century BC, Khirbet Qeiyafa inscription 10th century BC).
The first published group of Proto-Sinaitic inscriptions were discovered in the winter of 1904–1905 in Sinai by Hilda and Flinders Petrie. These ten inscriptions, plus an eleventh published by Raymond Weill in 1904 from the 1868 notes of Edward Henry Palmer, were reviewed in detail, and numbered (as 345-355), by Alan Gardiner in 1916. To this were added a number of short Proto-Canaanite inscriptions found in Canaan and dated to between the 17th and 15th centuries BC, and more recently, the discovery in 1999 of the two Wadi el-Hol inscriptions, found in Middle Egypt by John and Deborah Darnell.