We can all agree about the confusion we face trying to understand how a ruthless predator like a wolf could descend into something as harmless as a chihuahua or dachshund. The size, temperament and habits of modern dogs are incredibly different from that of their ancestors from nearly 20,000 years ago. This is due to the genetic changes that took place over time and caused the formation of different breeds. Not only did canines evolve into specific breeds, but each breed of canine also evolved in different ways. Much of this differentiation can be credited toward selective breeding for specific behavioral aspects; such as scent hunting, companionship, protector and so on. These differences can be observed in the evolutionary trends depicted in the image below.
The above image comes from a study on dog breeds and domestication, and depicts a genetic tree that shows the “genetic paths” breeds followed from their common ancestor, the wolf. The tree begins in the middle and stems out in nodes. The closer one node is to another represents larger amounts of genetic similarities. Here we’re able to see a path to how these popular modern breeds evolved. At the center of the tree there is the wolf and if you follow the tree outward, you can see it’s most closely related to the modern-day breed German Shepherd.
Even though they are the most closely related on the tree, the German Shepherd has proved to have a different brain composition than wolves. This is due to domestication and evolutionary changes related to biology. Still, noting their similarities, the German Shepard was not bred out from the wolf in terms of appearance as they have a body type that is more similar to wolves than that of other breeds.
Moving to the green circle, we begin to see dogs that greatly differ from wolves in terms of appearance. This circle contains the Walker Hound and Beagle. These breeds are much smaller than their wolf ancestors, with shorter limbs and smaller overall body compositions. These two breeds have been behaviorally bred to be “scent hunters.” Because of that, they follow similar genetic tree trends. Later factors, such as differences in looks, are the result of other selective breeding.
The blue circle contains the Pitbull, Boxer, and Labradors. These canines also differ greatly from wolves in terms of body composition. These breeds were bred for sport fighting, protection and police/military work. This behavioral aspect has been continually bred for and resulted in these breeds typically being used in working roles.
When backtracking from the blue circle, you can see the red circle shares a similar node (black dot). This black dot represents a common ancestor between the blue and red circles that occurred more recently than the wolf did. The red circle represents the Rottweiler and Great Dane, both of which have similar behavioral traits to breeds in the blue circle, yet they were bred out further in terms of looks.
While it may be hard to imagine that our loving canine companions are direct descendants of a once feared beast, genetic evidence helps us discover all of the steps it took to get from wolves to the breeds we know today. By following genetic patterns we can begin to understand not only where breeds came from, but also why they look and act the way they do.
