According to the findings of Hungarian and Swedish experts, modern dog breeds that are genetically more distant from wolves have a considerably greater brain size compared to ancient breeds that are thousands of years old.
Since the roles or life histories of the breeds cannot explain the rise in brain size, urbanization and a more complicated social environment are most likely responsible.
Even today, the 400 dog breeds that are currently recognized have evolved very quickly and display a wide range of characteristics, making them a gold mine for researchers interested in speedy changes within a species.
Since the human brain is extremely large in comparison to body size, scientists have long been interested in the factors that influence brain size. Comparing the various dog breeds can help answer some questions.
Is there a correlation between brain size and the specific tasks for which a breed was bred? Are there differences, for example, between lap dogs and hunting dogs? Or is it more influenced by life expectancy and the challenges of offspring rearing?
We can be sure that sustaining a larger brain is expensive because thinking and cognitive functions need a lot of energy.
The results show that the breeding of modern dog breeds has been accompanied by an increase in brain size compared to ancient breeds. We couldn’t explain this based on the tasks or life history characteristics of the breeds, so we can only speculate about the reasons. Perhaps the more complex social environment, urbanization, and adaptation to more rules and expectations have caused this change, affecting all modern breeds.
Enikő Kubinyi
László Zsolt Garamszegi, an evolutionary biologist at the Ecological Research Centre in Hungary, has been studying the evolution of brain size for a long time. “The brains of domesticated animals can be up to twenty percent smaller than those of their wild ancestors. The likely reason for this is that the lives of domesticated species are simpler compared to those of their wild counterparts. In the safe environment provided by humans, there is no need to fear predator attacks or hunt for food. Therefore, there is no need to sustain the energetically costly large brain, and the freed-up energy can be directed towards other purposes, such as producing more offspring, which is important for domesticated animals.”
Niclas Kolm, at Stockholm University, focuses on brain evolution and the link between variation in brain morphology and behavior. “Different dog breeds live in varying levels of social complexity and perform complex tasks, which likely require a larger brain capacity. Therefore, we hypothesize that the selective pressures on the brain can vary within the dog species, and we may find differences in brain size among breeds based on the tasks they perform or their genetic distance from wolves.”
It took decades to prepare the first in-depth investigation of the size of various dog breeds’ brains.
Tibor Csörgő, a senior research fellow at the Department of Anatomy, Cell and Developmental Biology at Eötvös Loránd University (ELTE), has been collecting skulls for decades. CT scans of the skulls were performed by Medicopus Nonprofit Ltd. in Kaposvár.
Based on the CT images, veterinarian Kálmán Czeibert reconstructed the brains and determined their exact volume. The Canine Brain and Tissue Bank, operated by ELTE for the past seven years, which enabled the verification of brain volumes calculated from skull images using actual brains, complemented this invaluable collection. In the end, information was collected from 865 people representing 159 different canine breeds, with 48 of those people being wolves.
Wolves have an average brain volume of 131 cm3 and an average body weight of 31 kg, according to research findings in the journal Evolution. Dogs of a similar weight have a brain volume that is only roughly 75 percent of that, or 100 cm3.
This confirms that domestication has also led to a decrease in brain size in dogs. The more a canine breed’s genetic separation from wolves, however, the higher its relative brain size increases, which astonished researchers. Contrary to assumptions, breeds’ initial purposes, typical litter sizes, and lifespan are unrelated to brain size.
“The domestication of dogs began approximately twenty-five thousand years ago, but for ten thousand years, dogs and wolves did not differ in appearance. Many ancient breeds, such as sled dogs, still resemble wolves today. However, the transition to settlement, agriculture, pastoralism, and the accumulation of wealth offered various tasks for dogs, requiring guard dogs, herding dogs, hunting dogs, and even lap dogs. However, a significant portion of the distinct-looking breeds known today has only emerged since the industrial revolution, primarily in the last two centuries, as dog breeding has become a kind of hobby,” says Enikő Kubinyi, a senior research fellow at the Department of Ethology at ELTE.
“The results show that the breeding of modern dog breeds has been accompanied by an increase in brain size compared to ancient breeds. We couldn’t explain this based on the tasks or life history characteristics of the breeds, so we can only speculate about the reasons. Perhaps the more complex social environment, urbanization, and adaptation to more rules and expectations have caused this change, affecting all modern breeds.”
Research has shown that older breeds, noted for their independence, are less aware of human cues and bark less, differing from modern varieties in their visual and audio communication patterns.
