Just as Yemen was and still is the Arab genealogical reference, its script was their reference script wherever they settled. However, it is safe to assume based on inscriptions that around the 9th and early 10th centuries BC, two well-formed alphabets with many common shapes and similar overall look and feel had existed in the greater Arabian Peninsula.
Nabateans added 6 symbols to the Aramaic alphabet to represent sounds that did not occur in Aramaic. One can not always conclude from a few found inscriptions when a specific script had started.
Inscriptions can not always determine, with absolute certainty, precise timelines of ancient scripts. Others changed their letter forms radically for the sake of connectivity, like cursive Musnad in Yemen and may be Pahlavi of Persia.
They wrote with a highly cursive Aramaic-derived alphabet that would eventually evolve into the Arabic alphabet. Photo: The basmalah "In the name of God the Merciful the Compassionate" - the opening words of the Quran is here done in an elaborate thuluth script with the letters joined so that the entire phrase is written without lifting the pen from the paper.
Like the people of Persia, they did not fully embrace monotheism until after the emergence of Islam The Arab tribes of the heartland were not isolated from the religiously turbulent north though.
This was probably due to its location on the trade route between Persia and the Roman Empire. In the early centuries of the first millennium, the northern area of the greater Arabian Peninsula was a land of several old and new religions.
Dumat al-Jandal is the earliest known northern Arab city dating back to the 10th century B. Like Arabic, their written texts consisted largely of consonants and long vowels, with variations on the same basic letter shapes used to represent a number of sounds.
Inscriptions further reveal that over a century later another alphabet, Aramaic, clearly a variant of Phoenician, was in use throughout the Fertile Crescent area and may be Persia. The Kufic script appears to be the older of the scripts, as it was common in the early history of Islam, and used for the earliest copies of the Qu'ran.