I don't think domestication has anything to do with dog aggression. Some humans are bitchier than others, some people get along better than others
As far as dog aggression goes I have one word. TERRIER.
But...if the question is why is the DA still there, if it's not actively being bred for? So why do terriers still have aggression issues in general, if it's not being bred for? Or is it? I'm just asking here...I don't know. For example: in Aussies, I'm seeing a complete change in temperament from what the breed *should* be. The dogs should be reserved with strangers...they're a suspicious breed...supposed to guard your ranch/farm/flock. Now I meet tons of enthusiastic, friendly, in-your-face, everyone-is-my-friend Aussies...and it's just not right. But it makes for an easier dog to live with.
Also I really feel other dog breeds aggression is down played next to the Pit Bull. Nordic breeds are notoriously dog aggressive. Yeah - sled dogs seem to get along okay but I think it's because they are too busy/tired to kill each other. But I hear all the time if you want to have Huskies or Malamutes you need to have opposite sex pairs because same sex has a tendency to be dog aggressive.
I've never heard of northern breeds having more DA...and it's not been my experience...I've always found them to be fairly easy going in groups of dogs.
Look at the flock guardian breeds, Great Pyrenees, Komondor, Ovcharka etc- all of these breeds come with warnings that they are fine as long as they know "who belongs in the flock" but again I've read it's really hard to introduce more dogs into the household.
But most of these breeds (well, with the exception of the GP, I'd say)...are actually used (or could be used) for what they're supposed to be used for...flock guarding. This gets away from the idea of the pit bull being DA when not being bred for the original purpose. I'm not saying everyone with a guardian breed is using them for such things...but I think many of the breeders are breeding with that in mind...that someone *might* use them for such purposes. Unlike apbt breeders...who would be appalled to hear that someone might be using them for the intended purpose.
Heck - how many German Shepherds are dog aggressive?
Well, they're not in the same category of livestock guardians...but I'd say that many herding breeds aren't keen on other dogs. Unlike the northern breeds brought up before, herders aren't bred to work with others...except for maybe one or two others on a farm/ranch. But they work independently...and they're usually suspicious of strangers...dog or human...like I mentioned before with Aussies. So I'm never surprised to see a DA GSD or other herder. My herders aren't super fond of other dogs, and prefer other herding dogs...because they leave each other alone.
The only reason we don't hear about other breeds killing other dogs is that it doesn't make good news and Pit Bulls are really popular right now.
Yeah, but most dogs...won't fight to the death. Seriously. I'm not sure most pit bulls would either, in the grand scheme of things...but most dogs do a lot of posturing, and the fights are never truly serious. Because when you're fighting over status, or resources...you don't want to end up dead. That doesn't work out well for ya...so most dogs don't want to take it that far.
I also do think a lot of bad behavior has to do with excess energy. Pit Bulls and terriers in general have a TON of energy and I've only met a few owners[I mean in person, with the dogs I have met.] who have been able to actually tap that energy and tucker their dogs out. I'm not saying a tired dog is too tired to be DA, but I think a tired dog would be less reactive if they were truly busy/tired all the time.
"I don't have any idea if my dogs respect me or not, but they're greedy and I have their stuff." -- Patty Ruzzo
"Dogs don't want to control people. They want to control their own lives." --John Bradshaw