Scholars trace the roots of most historical and modern alphabets in the Near East and Europe, including Arabic and Latin, to a single obscure script, namely the Proto-Sinaitic or Proto-Canaanite script. This presumed script was attested by Western scholars in the early 20th Century following the discovery in 1905-06 of a few, very short graffiti inscriptions at “Serabit el-Khadim” in the Sinai Peninsula and the subsequent discovery in 1999 of a few similar ones at “Wadi el-Hol” in the middle of Egypt. According to these scholars, Proto-Sinaitic was derived from the Egyptian Hieroglyphs writing system between 18th-15th Century BCE and was in use for centuries before the rise of the two major ancient alphabets in the adjacent greater Arabian Peninsula, Phoenician (13th Century BCE), and Musnad (9th-7th Century BCE).
In this paper, which primarily emphasizes shapes and scripts functional characteristics analysis, the author believes there is no solid evidence to conclude that Proto-Sinaitic was the parent script. The author further believes that Musnad and Phoenician started either as independent scripts over a relatively short time period, or as one script splitting into multiple ones over a relatively long period, to replace and visually preserve, at the same time, a predominant, concurrently-used older writing system: namely the Akkadian Cuneiform script. In either scenario, these early alphabets represented different iterations to mimic the Akkadian Cuneiform script, abstracting a selective set of syllables into simpler, easier to handle and remember linked shapes. Visual evidence reveals Cuneiform was their model parent script for a long period.
Abulhab, Saad D., "Cuneiform and the Rise of Early Alphabets in the Greater Arabian Peninsula: A Visual Investigation" (2018). CUNY Academic Works.