The brains of modern dogs are getting bigger  

The first detailed study that took decades

Dogs’ brains may be considerably smaller than wolves’, but new research shows that modern breeding methods have increased their size. Compared to ancient dogs, modern breeds that have been domesticated for 150 years have larger skulls relative to their body size. However, scientists do not know the reason.

Many studies have shown that the domestication of wild animals leads to the shrinking of their brains and this is attributed to the reduced need for brain function for survival.

Studying the skulls of 159 dogs and some wolves, they found that while a wolf’s brain is 24% larger than a dog of a similar size, the more genetically different the dog was from the wolf, the larger its brain was. The findings show that the domestication of dogs thousands of years ago may have shrunk parts of the dog’s brain associated with mating, hunting and survival, but at the same time modern domestication has activated cognitive development over the past century and a half.

Different breeds of dogs live at different levels of social complexity and perform complex tasks that require greater brain capacity. – Niclas Kolm, evolutionary biologist at Stockholm University in Sweden

Kolm hypothesized that certain dog breeds bred by humans for more complex tasks such as herding or sports would have relatively larger brains. However, this is not the case. In contrast, the only factor that seems to affect brain size in a modern dog is how different its genes are from those of the wolf. It doesn’t matter its breed, its size, or its lifespan.

Perhaps the more complex social environment, urbanization and adaptation to more rules and expectations caused this change affecting all races. – Eniko Kubinyi, Eotvos Lorand University, Hungary

The findings are consistent with the “social brain” hypothesis, the idea that large brains can evolve to better fit into complex social environments. Previous research, for example, had shown that dogs that were more closely related to wolves were worse at communicating with humans.

The scientists believe that to learn more about how the brains of modern dogs differ from wolves and ancient dogs, future research should focus on the size of specific parts of the brain.

The study was published in Evolution .