Semyonova, A, Aggressive dog breeds: Document nr. 1; Heritability of behavior in the abnormally aggressive dog, The Carriage House Foundation, November 2006.
Probably everyone understands that all of the dog breeds we have created are a result of our own manipulation of inherited physical traits. Until recently, most of us recognized that much of the behavior of pure bred dogs is also a result of manipulating inheritance: if you want to do sheep trials, you get a border collie; if you get a beagle, he will likely become instantly deaf to your calls if he picks up a scent to track. Once the discussion started about perhaps banning breeds that, as a breed, have a high tendency to attack and kill, everything got confused. People started to dispute the heritability of any kind of behavior in dogs, let alone killing behavior. To clear up the confusion, and to bring us back to the realities, we need to understand how it is, in fact, possible for behavior to be inherited. Only then can we have a clear and honest discussion about the problem of killing aggression in domestic dogs. First we have to understand a couple of biological concepts. Then we will look at recent research on the physical (thus heritable) mechanism behind abnormal aggression in dogs. In the end, the heritability of certain behaviors in certain domestic dogs is the result of a combination of what biologists call “physical conformation” and “behavioral conformation”, often combined with – sometimes on purpose, sometimes inadvertently – selecting for real and/or pathological abnormalities in a breed. In this document, I will give a short summary of how this works. Bear with me, it all comes together in the end with reference to aggressive dog breeds.
Physical conformation means that the dog has been bred until he is physically shaped specifically for the task we want him to perform. His body – brain, skeleton, muscles, metabolism, heat economy – will be different from other dogs, better adapted to the task we have invented for him. Basically, this just means the physical positions the dog has to assume to do his job will feel good and comfortable to him. The border collie is physically designed for the stalking stance and for switching easily from standing to lying down to standing again (with a frequency that would cause acute arthritis in any other breed), because his skeleton and muscles have been adapted to do these things easily and without damage…