I just bought this book, “From Camel to Truck: the Bedouin in the Modern World“, by Dawn Chatty, one of the foremost authorities on nomadic societies and migrations. I will tell you what I think when I read it.
A friend who is around fifty years old just told me that he used to ride the grey mare who is the grand-dam of the chestnut Abu Junub colt when he was young, and that his grand-father had bought the original Kuhaylat Umm Junub mare from the Bedouins on the basis that she was asil, and on the basis of her hujjah which he said contained the seals of tribal Bedouin shaykhs. He said they had bought the original mare from Ibn Rakhis of Shammar who was settled in Rafha to the north of Hafr al-Batin. He also told me that they will look for her hujjah and if they find it, they will give me a copy. So fifty years ago, the tail female of the few Abu Junub horses now in Saudi Arabia were were with Ibn Rakhis from Shammar.