This is very interesting. The picture included here is just one example of the radical changes that have been introduced into dog breeds – and not necessarily for the better.
For the sake of honest disclosure, I will admit to owning “purebreds” (the ‘pureness’ of purebreeds is a discussion for another time) but I also have mutts. All the dogs I’ve had since childhood had a few things in common, they were crazy, prey driven, ball-crazy, intense, motivated, athletic (crazy dogs are easier to train) and none had intentionally bred defects. I would never buy/adopt a dog whose breed characteristics exacted a health burden.(Asher 2009). That just incentivizes people to breed more of these intentionally unhealthy animals.
The dogs on the left are from the 1915 book, ‘Breeds of All Nations‘ by W.E. Mason. The examples on the right are modern examples from multiple sources. To be able to make an honest comparison, I’ve chosen pictures with similar poses and in a couple of cases flipped the picture to get them both aligned in the same direction. I had to skip some breeds I wanted to include because of the lack of detail in the older photographs.
It seems incredible that at one time the Bull Terrier was a handsome, athletic dog. Somewhere along its journey to a mutated skull and thick abdomen the bull terrier also picked up a number of other maladies like supernumerary teeth and compulsive tail-chasing.
See other examples of the effects of pure breeding: 100 Years of Breed “Improvement” | Science of Dogs.