The first verifiable kingdom of great power to rise in Ethiopia was that of Axum in the 1st century CE. It was one of many successor kingdoms to Dʿmt and was able to unite the northern Ethiopian Highlands beginning around the 1st century BCE. They established bases on the northern highlands of the Ethiopian Plateau and from there expanded southward. The Persian religious figure Mani listed Axum with Rome, Persia, and China as one of the four great powers of his time. The origins of the Axumite Kingdom are unclear, although experts have offered their speculations about it. Even who should be considered the earliest known king is contested: although Carlo Conti Rossini proposed that Zoskales of Axum, mentioned in the Periplus of the Erythraean Sea, should be identified with one Za Haqle mentioned in the Ethiopian King Lists (a view embraced by later historians of Ethiopia such as Yuri M. Kobishchanov and Sergew Hable Sellasie), G.W.B. Huntingford argued that Zoskales was only a sub-king whose authority was limited to Adulis, and that Conti Rossini's identification can not be substantiated.