Dog Skull Analysis Rewrites Evolution of Humanity’s Best Friend

Dog skull analysis rewrites the evolution of humanity’s best friend

By Kate Wong edited by Clara Moskowitz

Modern dog breeds come in a bewildering array of shapes and sizes: from Chihuahua to Great Dane, Corgi to Greyhound, Pug to German Shepherd. Indeed, the domestic dog, Canis familiaris, shows more variation in its physical characteristics than any other mammal species on Earth. Conventional wisdom has it that this extreme variation is the result of humans intensively breeding dogs for particular traits over the past 200 years. Now, a new analysis of the skulls of modern and ancient dogs and wolves has turned that idea on its head, revealing a much older origin of canine diversity.

Archaeologists have long been interested in the evolution of dogs because this species is believed to be the first animal domesticated by humans. Evidence indicates that dogs evolved from wolves and were domesticated at various times and in different parts of the world. From there, the story becomes more difficult to discern because the record of ancient dog remains (including any DNA or other molecules that may have been preserved) is spotty. Although some archaeological evidence suggests that the first domestic dogs may date back 33,000 years or more, ancient DNA analyzes place the origin of our canine companions at more than 11,000 years ago. Regardless, scientists didn’t think the characteristics of early dogs were particularly variable. It wasn’t until people began intensive breeding programs in the mid-1800s that dogs began to transform into wildly different forms — or so the story goes.

In the new study, Allowen Evin of the University of Montpellier in France and colleagues analyzed hundreds of dog and wolf skulls spanning the past 50,000 years. The oldest skull in their sample with definitive dog features dated to nearly 11,000 years ago, matching DNA estimates from when dogs evolved from wolves. What is surprising is that researchers discovered great diversity in the size and shape of dog skulls among the first specimens studied. Although these characteristics did not reach the extremes seen in modern breeds, such as bulldogs, with their squashed faces, and borzois, with their ultralong snouts, these ancient dogs had half the diversity of modern dogs, much more than expected.

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The results indicate that humans were not the sole driving force behind dog evolution, as previously thought. Other factors, such as climate or geography, may have contributed significantly to making humanity’s best friend the extraordinarily diverse species it is today.

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