Task: Question Answering
Input (English): Passage: Ethiopian historians such as Taddesse Tamrat (1935–2013) and Sergew Hable Sellassie have argued that modern Ethiopian studies were an invention of the 17th century and originated in Europe. Tamrat considered Carlo Conti Rossini's 1928 Storia d'Etiopia a groundbreaking work in Ethiopian studies. The philosopher Messay Kebede likewise acknowledged the genuine contributions of Western scholars to the understanding of Ethiopia's past. But he also criticized the perceived scientific and institutional bias that he found to be pervasive in Ethiopian-, African-, and Western-made historiographies on Ethiopia. Specifically, Kebede took umbrage at E. A. Wallis Budge's translation of the Kebra Nagast, arguing that Budge had assigned a South Arabian origin to the Queen of Sheba although the Kebra Nagast itself did not indicate such a provenience for this fabled ruler. According to Kebede, a South Arabian extraction was contradicted by biblical exegetes and testimonies from ancient historians, which instead indicated that the Queen was of African origin. Additionally, he chided Budge and Ullendorff for their postulation that the Aksumite civilization was founded by Semitic immigrants from South Arabia. Kebede argued that there is little physical difference between the Semitic-speaking populations in Ethiopia and neighboring Cushitic-speaking groups to validate the notion that the former groups were essentially descendants of South Arabian settlers, with a separate ancestral origin from other local Afroasiatic-speaking populations. He also observed that these Afroasiatic-speaking populations were heterogeneous, having interbred with each other and also assimilated alien elements of both uncertain extraction and negroid origin. 
Question: What are the two groups Kebede argued were were essentially descendants of South Arabian settlers, with a separate ancestral origin from other local Afroasiatic-speaking populations?
Output (English): Cushitic-speaking groups.