Originally Posted by Suki Wingy
What people don't realize is the idea of "breeds" is relativley new, within the last two or three centuries. Before that their were "types" of dog. Outcrosses were very common. A dog was either defined by its job, its location, its founder, or a combonation of them. For example, a "pointing dog" or a flushing breed. Some got general characteristics, like the "bengal harrier" was a spotted harrier. It made no difference wether someone crossed in some birddogs or mastiffs somewhere, as long as it could do its job.
I like to make the comparison to horse breeds. Sure you have your pure bred registries like the Jockey Club, APHA, and AQHA, but you also have types based on the job they were bred to do or a similar characteristic. For example, hunter/ jumper, dressage, cob, etc.
There will always be a large discrepancy in terriers because of the way the breeds were formed. Breeds sprung up very localized, and all terrier breeds are very related. I think of most working terrier breeds as extreme specialization of the same breed.