Everyone has tried it at one time or another: attempting to identify a dog’s breed by its physical appearance. With purebred dogs the task can be easy—Dalmatians sport the classic spots, Pomeranians are a distinctive ball of fur. Even breeds with more variable appearances, Australian Shepherds, Greyhounds, Pointers, generally hold true to their breed’s distinctive physical traits. But guessing the ancestry of a mixed-breed dog is a lot harder than it looks.
Research conducted by the Broad Institute in Cambridge, Mass., in conjunction with the International Association of Animal Behavior Consultants, recently asked participants to identify the top three ancestral breeds of 31 mixed-breed dogs presented in an online survey. Overall accuracy for correctly guessing the dogs’ ancestry averaged only 25%. The self-identified dog professionals scored slightly higher, averaging 28% correct answers. The findings are in keeping with a number of similar studies, adding further proof that the unscientific assessment of a mixed-breed dog’s heritage based solely on appearance is correct just one-quarter of the time.
An online search will turn up many sites offering “tips on how to identify the breeds in a mixed-breed dog,” and even apps that purport to identify dog breeds from photographs. All of these methods rely on visual references and here’s why this approach is flawed.
A dog’s physical appearance is largely controlled by a small number of genes so it’s important to understand dominant vs. recessive genes. Recessive are those you need to inherit two copies of to show the trait and dominant you only need one. Traits such as a black coat, short hair, or drop ears might make you think of some of the more popular breeds with these same features. But dominant traits such as these, just by the very nature of being dominant, can be attributed to many breeds beyond the one you’re thinking of. Likewise, traits that are recessive such as a long coat, prick ears, or tan points that are associated with a specific breed, may not make it past the dominant ones in a mixed-breed and therefore can’t be seen.
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The way a dog expresses visually the different breeds in its ancestry can vary greatly depending on what dominant traits and/or recessive traits a dog receives from its parents.
The mystery that makes up mixed breed canine ancestry is summed up by a quote that appears on one of the academic research project’s home page: Appearances are a glimpse of the unseen (credited to the Greek philosopher Anaxagoras).