“A dog (Olde English Bulldog) that looked much like today’s pit bull was originally used in the 1800’s in the British Isles to ‘bait’ bulls. These matches were held for the entertainment of the struggling classes; a source of relief from the tedium of hardship. In 1835 bull baiting was deemed inhumane and became illegal, and dog fighting became a popular replacement. Soon, a new bulldog was created by crossing the Olde English Bulldog with terriers to create smaller, more agile dogs.”
http://www.badrap.org/breed-history
Many, many other sources of information available.
Your link states: “Recent research including DNA analysis by Dr. Victoria Voith and others has proven that dogs commonly identified as pit bulls are quite often a mix of multiple breeds, so breed identification by appearance alone is now considered to be inaccurate and misleading.” That does not mean that the “American Pit Bull Terrier” (APBT) is a mix of multiple breeds any more than the German Shepherd Dog or other breeds are a “mix.” That is how dog breeding works, with breeders introducing different blood lines to improve their breeds.
If DNA analysis is performed on any dog, even a pure-bred one, similar ambiguous results do appear.
So this article does not prove anything about the origin of the breed. There is likely truth to the assertion that the origins of the APBT stems from the bull fighters of the early nineteenth century, with the addition of Terrier genes. I do not know how much of the Olde English Bulldog is in the bloodline of the modern APBT. Nevertheless the modern APBT breed (UKC) is over 120 years old. Besides, the issue at hand is not the origin of the APBT.
The issue is wether the dog in question here, an American Bulldog, has Pit Bull Terrier in it, NOT wether the APBT has American Bulldog in it. And no one has shown me any evidence that the American Bulldog has APBT in it.
An excellent synopsis and discussion of these issues can be found in Vicki Hearne’s piece “ Lo the American Pit Bull Terrier.” It can be found in her book, “Adam’s Task.” Chapter 9, page 192, you can read a lot of it free on Amazon.
That said, my experience has been that the American Bulldog, as well as the APBT can be quite dog aggressive and should not be allowed contact with other dogs without close supervision.