Read about this experiment a few years back.





Point is, you can breed in "tameness" as well as aggressive behavior.

I believe that Pit Bulls are inherently more on the aggressive side. Perhaps there is are genetic lines of pit bulls that are more domesticated, coming from genetic lines that are good family dogs, good with kids, etc. But the flip side is that in many other genetic lines, the aggressiveness has been enhanced, and then the human interaction and training that these more aggressive lines experience makes them even more dangerous and unpredictable.

Counter this with the golden retriever. My family is on our second one. They are gentle and non-aggressive to a fault. Could you breed an aggressive Golden? Could you train one to be aggressive or would an abused dog be more aggressive? I'm sure the answer is yes... but the starting point on the aggressive scale for pit bulls is much further over to the wild side.