See the Wonderful Ethiopians of the Ancient Cushite Empire, especially, Chapter VIII:
VIII. ARABIA AND HER ANCIENT RACES.
1. Ancient Arabia Part of the Cushite Empire.
2. Divisions of Arabia, Deserta, Felix and Petrae.
3. Arabia Settled by Two Distinct Races
4. The Cushite-Arabians were Civilized Agriculturists.
5. The Semitic-Arabians were a Wild, Nomadic Race.
6. The Cushite-Arabian was the Oldest and Purest Blood.
7. The Rise of Mohammed and the Koreysh.