They may be man's best friend, but could we have created dogs in our own image?
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Scientists say that by selectively breeding the animals for certain behaviours, humans have shaped their brains.
Over several hundred years, people have bred different lineages of domestic dogs for different tasks, such as hunting, herding, guarding or companionship.
A study published in the JNeurosci, the Journal of Neuroscience, examined whether and how selective breeding has altered the gross organisation of the brain in dogs.
Erin Hecht, from the department of human evolutionary biology at Harvard University, and colleagues analysed magnetic resonance imaging (MRI) scans of 62 male and female dogs of 33 breeds.
The research team observed wide variation in brain structure that was not simply related to body size or head shape.
Scientists examined the areas of the brain with the most variation across breeds which included beagles, dachshunds, greyhounds and Labrador retrievers.
This generated maps of six brain networks, with proposed functions varying from social bonding to movement, that were each associated with at least one behavioural characteristic.
The variation in behaviours across breeds was correlated with anatomical variation in the six brain networks, researchers say.
Importantly, a phylogenetic analysis - looking at evolutionary relationships - revealed most change has occurred in the terminal branches of the dog phylogenetic tree, indicating strong, recent selection in individual breeds.
Researchers say these results establish that brain anatomy varies significantly in dogs, likely due to human-applied selection for behaviour.
The authors write: "These results indicate that through selective breeding, humans have significantly altered the brains of different lineages of domestic dogs in different ways.
"Finally, on a philosophical level, these results tell us something fundamental about our own place in the larger animal kingdom - we have been systematically shaping the brains of another species."
In all six of the networks, the scientists found significant correlations with at least one behavioural specialisation.
For example, Network 2, which involves regions that support higher-order olfactory processing, shows a significant correlation with scent hunting, they say.
Network 3, which involves regions that support movement, eye movement and spatial navigation, shows a significant correlation with sight hunting, they added.
Australian Associated Press
