Dog Brains Have Unexpectedly Grown Larger, Scientists Discover

Although wolf brains are substantially larger than dog brains, recent study indicates that contemporary breeding practices have somewhat boosted the relative size of dog brains.

Modern dog breeds that have emerged in the last 150 years have bigger heads proportion to their body size than historic varieties had. But researchers are still baffled as to why.

The proportional size of the brains of domesticated wild animals, such as dogs, fish, pigs, cattle, sheep, rabbits, and cats, is drastically reduced. This has been demonstrated in several studies.

According to scientists, this is a reaction to a decreased demand for cognitive power for survival.

But when scientists compared the skulls of 159 dog breeds, including some wolves, they made an unexpected discovery.

Even if a wolf's brain is 24% bigger than a dog of comparable size, genetically speaking, the more a dog breed varied from a wolf, the bigger their brain.

According to the research, while dog domestication thousands of years ago may have originally caused some areas of the dog's brain to shrink, such as those connected to partner selection, predators, or hunting, current breeding has resulted in a little amount of cognitive gain during the past 150 years.

Yet how?

"Different dog breeds live in varying levels of social complexity and perform complex tasks, which likely require a larger brain capacity," claims evolutionary scientist Niclas Kolm of Stockholm University in Sweden.

Kolm and his associates therefore proposed the theory that those dogs with human breeding for more intricate jobs, such as herding or sports, would have larger relative brains.

That wasn't the situation. Not the purpose of the breed, its litter size, or life expectancy, but rather how divergent their genes were from wolves proved to have an influence on the relative brain size of current dog breeds.

In reality, scientists were unable to detect any variation in the relative size of the brains in the breeds listed by the American Kennel Club.

The absolute brain size of individual dogs was found to affect their memory and self-control in previous research, but this effect doesn't appear to be powerful enough to affect the relative brain size of their breed as a whole.

Other recent research that reveals the behavior certain dogs are bred for is not inherent in their genetic makeup also supports the findings of the present study.

Enik Kubinyi, an ecologist from Hungary's Eötvös Loránd University, hypothesizes that "possibly the more complex social environment, urbanization, and adaptation to more rules and expectations have caused this change, affecting all modern breeds."

This is consistent with the social brain theory, which holds that big brains may develop to adapt to increasingly complicated social settings.

For instance, prior studies have shown that dogs that are more closely related to wolves are less adept at connecting with people.

The team advises that future study should examine the size of various brain areas to understand more about how ancient and contemporary canine brains vary from wolves.

Then researchers might be able to determine what effect humans have had on canine cognition and behavior.

The study was published in Evolution.