Wolves were domesticated only once, in what is now China, about 11,000BCE.
Oh, not even then. The most primitive cousins of domesticated dogs are probably the American Dingo, the xoloitzquintle (before they went bald), the Canaan Dog (sigh), the South Korean Jindo Dog (rightfully regarded as a national treasure), the Asiatic dhole (cute), the African wild dog (they eat each other's vomit), the jackal (almost forgot), and so on. The ancestors of the domestic dog probably diverged from the wolves before we even climbed out of the trees. Their other relatives just got whacked by the Ice Age.
This process was never repeated.
Except when our dogs ran out into the wilderness to mate with their distant relatives, producing the spitz breeds, for example.
Another [dog bred for alpha personality] is the pitbull, developed to fight other dogs.
Nah, they're just dumb blockheads. You get more bonafide alpha-character in the Dobies. Dobies just have better manners. Ironically, you can be safer
with a Dobie at your throat than
without. The owner could be some elderly drunkard with a gun. In some neighborhoods, the cops will shoot at you just for having the wrong color skin. A Dobie, though, isn't going to dig into you as long as you lay still. As long as that Dobie thinks he has you under his control, you couldn't be safer in your mother's arms.
The rottweiler was originally developed in Roman times to pull carts in mountainous country where horses weren't appropriate.
Well, that can explain why the dog can be very stubborn in the face of resistance and tends to respond well to praise. Pulling weight is mostly just mental, you know. Pitbulls have that trait, too. It's not so much dominance instincts as pure, mental perseverance. They simply don't back down.
Anyway, the alpha gene...
Okay, is it really that black-and-white? If it's based on a tandem-repeat similar to the promotor region for gene that codes the dopamine receptor D4, for example, there would be a higher degree of variability. We have another problem. Stubborness and dominance are not the same thing, and the same goes for violent behavior. The Dobie's need for control, in my mind, is a lot closer to true dominance. Even though you're more likely to be bitten by a
Cocker Spaniel than a Dobie, their personalities are more powerful and intense than any breed I have ever encountered, period. So I'm not sure if you're really referring to one particular gene or referring to an apparent phenotype that could be the result of many
different interacting genes.