The first post-diluvian civilization, probably.
Let’s not forget that Abraham had other children besides Ishmael and Isaac, by his concubines. They were sent ‘to the east’ with gifts and goods after Sarah died and Isaac was old enough to take care of the family’s fortune ...................
The Death of Abraham (NIV)
25 Abraham had taken another wife, whose name was Keturah. 2 She bore him Zimran, Jokshan, Medan, Midian, Ishbak and Shuah. 3 Jokshan was the father of Sheba and Dedan; the descendants of Dedan were the Ashurites, the Letushites and the Leummites. 4 The sons of Midian were Ephah, Epher, Hanok, Abida and Eldaah. All these were descendants of Keturah.
5 Abraham left everything he owned to Isaac. 6 But while he was still living, he gave gifts to the sons of his concubines and sent them away from his son Isaac to the land of the east.
7 Abraham lived a hundred and seventy-five years. 8 Then Abraham breathed his last and died at a good old age, an old man and full of years; and he was gathered to his people. 9 His sons Isaac and Ishmael buried him in the cave of Machpelah near Mamre, in the field of Ephron son of Zohar the Hittite, 10 the field Abraham had bought from the Hittites.[a] There Abraham was buried with his wife Sarah. 11 After Abraham’s death, God blessed his son Isaac, who then lived near Beer Lahai Roi.