Hell they couldn’t have even been a mixture of the two because Arabs (or at least the Caucasoid ones that we’re familiar with now) ain’t even that old to begin with and didn’t really appear til around 6,000 years ago (conveniently around the time Cacs came into existence)....Compare that to 10,000 years of Dynastic Kemet with 90,000+ years of Pre-Dynastic Kemet and the fact that Black People were the first to walk on this Earth more than 200,000 years ago and it’s easy to do the math.
Plus the Ancient Egyptians never went extinct. This ain’t directed at you but everybody including Black folks need to stop treating them like they were some mysterious race of people that suddenly vanished after 525 BCE and realize that they were a multitude of African ethnicities or “tribes” and they can be found in many groups within East Africa, West-Central Africa, North Africa, Southern Africa, and even within the Diaspora to this very day. The Kushytes/Nubians too as a matter of fact, you can look to India, Arabia, and East Africa to find their descendants.
Some good books on this subject are:
God wills the Negro by Theodore P. Ford
Exiled Egyptians by Moustafa Gadalla
Wonderful Ethiopians of the Ancient Cushyte Empire by Drusilla Dunjee Houston
When The World Was Black Pt. 1 and 2 by Dr. Supreme Understanding
Egyptian Language by Dr. Clyde Winters
Nile Valley History and the Rigveda by Dr. Clyde Winters
The Kushytes: Who, What, When, Where by Dr. Clyde Winters
Black Man of the Nile and His Family by Dr. Ben Jochannan
Sacred Symbols of the Dogon by Laird Scranton