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Can DNA Decipher the Mix?
Unraveling the genetic tapestry provides clues to breeds and their mixes
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A mongrel dog is like a box of chocolates: You never know what you’re going to get. And therein lies the appeal. What’s more fun than serendipitous unpredictability all bundled up in puppy fur? But when that puppy grows up, we inevitably make assumptions about her ancestry based on how she looks and behaves. Our logic goes like this: “If my pooch is long and low to the ground, and she never barks, she must be a Corgi/Basenji mix.”

But it’s much more complicated. The genes—and there may be hundreds—that work together to make a Corgi look like a short-legged Shepherd may be completely different than those responsible for a Basset Hound’s low-slung carriage. With some exceptions, scientists cannot yet connect genetic dots to specific traits. But they have discovered something tangible that measures some of the differences between breeds: genetic patterns of organization displayed on a scatter graph that answer the question, “What’s the same and what’s different?”

A scatter graph provides a symbolic visualization of DNA, wherein each individual dog contributes one point. The resulting pattern indicates the type and strength of the relationship between individuals. The more the points cluster around each other, the more alike they are.

 

Breakthrough
Until only a few years ago, scientists couldn’t identify the differences in genetic material that might explain profound variations in the Canidae clan. From wolf to West Highland White Terrier—they all looked the same under the microscope. Then, in 2004, Elaine Ostrander and her colleagues at the Washington-based Fred Hutchinson Cancer Research Center published data indicating that as much as 30 percent of the dog’s genetic material accounts for breed variation (Science, May 2004).

In addition to simplifying methods used to find markers for breed-related disease, the researchers identified patterns of “breedness” and tracked the history of breed DNA. At the same time, by following mitochondrial DNA, genetic material passed down from mother to offspring without changing, they traced the breed’s journey.

Depending on how much time is attributed to a generation and how many generations are involved, scientists can estimate how much time has passed. Based on this tracking, it has been suggested that it took 5,000 years to develop and refine a handful of the world’s 350-plus breeds, and about 400 years to create the rest.

Research indicates that four distinct breed groups are ancient: (1) Middle Eastern Saluki and Afghan, (2) Tibetan Terrier and Lhasa Apso, (3) Chinese Chow Chow, Pekingese, Shar-Pei and Shih Tzu; Japanese Akita and Shiba Inu, (4) Arctic Alaskan Malamute, Siberian Husky and Samoyed. Although the 13 breeds look different, they are so closely related that they are represented by a single genetic cluster. It’s likely they all originated from the same stem-parent—proto-breed, if you will—who roamed the Asian continent.

As humans migrated from one place to another, this ubiquitous proto-breed trotted along, bringing with her the ingredients needed to cook up all the breeds we’re familiar with today. Her offspring performed work unique to each geographical region, such as hunting, hauling or guarding. Isolated and mating only with each other, “accidental” breed types exhibiting consistent shape, color and behavior emerged.

No matter what historians might claim—scent hound to sight hound, bird dog to bad dog—evidence produced through genetic research indicates that all remaining breeds have been concocted in the last 400 years. Although closely related to one another, they can be identified as distinct based on the way their DNA separates.

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