I know some areas have probably had an Arabic majority for a long time, like the Arabian Peninsula. I also know that other groups exist in the Middle East, like Persians, Turks, Kurds, etc.
From what I've read, though, Arabs are the largest ethnic group in West Asia. Have they always been a conspicuously large, if not a majority, even in Biblical times? Or did their population swell only after the conquests of Islam?
In areas that don't have an Arab majority (Turkey, Iran), does a significant amount of the population have any Arab blood?
Unfortunately I don't think this an answerable question. "Arab blood" does not define Arabness. Arabness is at least partially a linguistically defined ethnicity. That's why dark-skinned dark-eyed Anwar Sadat is just as much an Arab as light-skinned blue-eyed Bashar al-Assad is an Arab.
Aside from that definitional issue, our earliest sources, including biblical references, are to "Saracens", not Arabs. It's not at all clear who is being referred to when these classical sources are referring to Saracens. For instance while some sources might be using it in the sense that we mean of "ethnicity", and therefore define the area of territory occupied by Saracens broadly, others are using an unusually narrow definition, where, for instance, Saracens are the people who live in one very specific place. This can easily be misrepresented by Arab nationalists in cumulative fashion as suggesting that some huge portion of the Middle East was meaningfully "Arab" from a very early period. Maybe. I'm hugely, hugely skeptical.
Most of the writers we're relying on for these descriptions in the classical era have never been to the Middle East, have no idea who lives there, and the picture will remain fuzzy until the Arab conquests themselves.
I think the best we can probably do is to say that there were strong tribal connections throughout the region. Quite good linguistic connections. But making definitive statements in terms of percentages for ethnic populations is just not possible.
