I don't recall where I read about it since it was years back, but the theory was sound. Even whites (another place I don't recall where I read) came to the same conclusion. This was before we figured out DNA. The idea was that if you used pure say Arab blood and a black woman you'd end up with 50/50, then 75/25, 87.5/12.5 etc until you would eventually have 99.9% Arabs. They either cut that short and didn't keep it going for enough generations, or there were some genes introduced that wouldn't go away. Either way it blew up in their face.