He argues that the interpretations were based on the later presence (after Ghana's demise) of nomadic interlopers on the assumption that they were the historic ruling caste, and that the writers did not adequately consider contemporary accounts such as those of al-Yakqubi (872 A.D.) al-Masudi (c. 944 A.D.), Ibn Hawqal (c. 977 A.D.), al-Biruni (c. 1036 A.D.), as well as al-Bakri, all of whom describe the population and rulers of Ghana as "negroes".