I agree the cranial and maxillofacial anatomy of all dogs are the same. It's the muscles that control the jaws that differ greatly. Aw, I lied already. Bulldogs have wider jawsets than any other breed.
In bulldogs - and notice I'm not painting pits in any of these posts - cute little puppies are BORN with this:
This is certainly not to suggest any intentional breeding such that massive jaws are selected for in any subset of bulldogs. Coincidental at best.
Perhaps this massive jaw muscle has weaknesses... much like a swimmer might develop a muscle cramp. If a physical attribute is overdeveloped via close inbreeding, and when overtaxed, it cramps involuntarily.. certainly the swimmer didn't intend to drown because his legs wouldn't unlock.
I know my calves have cramped on me, and not a damned thing I could do about it until whatever chemicals I worked out instructed them to 'relax'.
I should probably add that conditions like hip dysplasia and such probably didn’t exist in the original breeding stock. Overdevelopment of desired characteristics via too close inbreeding produces physical problems. Why couldn’t ‘inability to control jaw muscles in the short term’ be one of them?
Muscles are incapable of locking; cramping, while a common affliction of muscles, is not the same as locking.
A rottweiler or German shepherd has greater bite force than an American staffordshire terrier, and no one makes the ludicrous argument that their jaws lock. What these breeds have in common is that they have all shared the spotlight of “Devil Dog of the Decade”. Currently, it’s the AST’s turn. In time, there will be a new culprit.
But so long as people parrot myths about dogs, this decades old problem will not be solved.
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The Locking Jaw
The most common myth about ‘pit bull’ dogs is that their jobs lock. This is untrue.
Breeds like the American Pit Bull Terrier do have very powerful jaws, and this is where this myth comes from. However, the jaw does not ‘lock’ - and you cannot get the jaw to ‘lock’ through abusive actions such as breaking the jaw. (yes, we have heard from people who believe this is how you get a ‘locking jaw’ and we have incredibly sympathy for any animals they own.)
On this topic Dr. 1. Lehr Brisbin of the University of Georgia wrote:
“The few studies which have been conducted of the structure of the skulls, mandibles and teeth of pit bulls show that, in proportion to their size, their jaw structure and thus its inferred functional morphology, is no different than that of any breed of dog. There is absolutely no evidence for the existence of any kind of “locking mechanism” unique to the structure of the jaw and/or teeth of the American Pit Bull Terrier.”
The ‘pit bull’ has powerful jaws, but they are not alone in this. This is yet another myth - that ‘pit bulls’ are more dangerous because they have the most powerful bite. Most large breeds and cross breeds have a very strong bite, and even smaller dogs can inflict a bite powerful enough to kill. Any dogs can be dangerous in the hands or an irresponsible, negligent or abusive owner.
http://www.dogwatch.net/myths/lock_jaw.html