This is josephus' explanation for how the cushites and berbers came to occupy east africa and libya respectively. This is also found in the bible.
“Abraham after this married Keturah with whom 6 sons were born to him…. Now the sons of Sous were Sabathan and Dedan. The sons of Dedan were Latusim, and Asur, and Lehum. The sons of Madian were, Ephas, and Aphran, and Anoch, and Abidas, and Eldas. Now for all these sons and grandsons Abraham contrived to settle them in colonies; and they took possession of Troglodytes, and the country of Arabia the Happy, as far as it reaches to the Red Sea. It is related of this Aphran that he made war against Libya, and took it, and that his grandchildren, when they inhabited it, called it from his name Africa.” (Antiquities of the Jews by Josephus, from the chapter entitled - “How the Nation of the Troglodytes were Derived from Abraham by Keturah”
Dana marniche-
"Our exploration starts with Josephus who following the Hebrew writings tells us that in his time the descendants of Keturah or Qeturah coming from southern Arabia had settled the area of the “troglodytes” in the Horn of Africa, which in Josephus' era was also considered part of "Arabia".
John Murray states the following.
“Josephus ('A.J.' i. 15) tells us that the descendants of Keturah occupied the Troglodyte country and Arabia Felix, which statement is repeated by Jerome ('Qu. Heb. in Gen.').” The Holy Bible according to the authorized version(A.D.1611) published 1872.
John murray is a white colonial historian
It is interesting to note that east africa was by greeks called arabia(anything east of the nile) and india minor. Arabia was also called ethiopia and india. India itself was called eastern ethiopia or straight-haired Aethiopians. These regions were by the greeks considered a racial continuation. I shall provide the sources duly.