Since independence, the population has been almost entirely Arab. However, there are Afro-Arab concentrations in western coastal locations, South Asians in southern regions, and small European communities in major metropolitan areas. Many ethnologists contend that the purest "Arab" stock is to be found in Yemen. Classified as Joktanic Semites, the Yemenis claim descent from Himyar, great-grandson of Joktan, who, according to the book of Genesis, was descended from Shem, the son of Noah. Yemenis were prominent in the early armies of Islam and thus helped to Arabize much of the Middle East. The Tihama has been subjected to occupation and infiltration by many conquerors, and its people show significant admixtures of other racial types, including Negroid peoples. A small minority of Akhdam perform menial tasks throughout the country. The history of the Yemenite Jews predates by centuries the Islamic Hijra ( AD 622). How they came to settle in the region has not been determined.