How dogs became companions

From ancient skulls to shifting genomes, new research reveals how deeply dogs and humans evolved together

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From village dogs to toy poodles to mastiffs, dogs come in an astonishing array of shapes, colours and sizes. Today there are estimated to be about 700 million dogs living with or around humans.

For many, dogs are loyal companions, working partners, and beloved family members, with the histories of our species deeply woven together. But how did this incredible diversity come to be and how far back does this relationship with humans go?

Two new studies published in Science provide some answers.

One, led by Allowen Evin from the University of Montpelier, draws on ancient skeletal remains. The other, led by Shao-Jie Zhang from the Kunming Institute of Zoology, draws on the study of DNA from ancient Eastern Eurasian dogs.

Together, these studies suggest the story of dogs and their relationship with humans is older and more complex than once thought.

Origins of dog diversity

The study by Evin and her colleagues used 643 dog and wolf skulls spanning the past 50,000 years to address the origins of modern dog diversity. Her team's analysis suggests the distinctive “doglike” skull shape first arose around 11,000 years ago, during the Holocene epoch, the time since the most recent ice age. They also found substantial physical diversity in dog skulls from the same period.

This means the wide range of shapes and sizes dogs have today isn't solely a product of the intense selective breeding programs that became popular in the last few centuries. Some of that variation emerged millennia earlier.