According to the research conducted by Hungarian and Swedish scientists, it has been observed that modern dog breeds, which are genetically more distinct from wolves, tend to have larger brain sizes compared to ancient breeds that have existed for thousands of years. This increase in brain size cannot be solely attributed to the roles or characteristics of the breeds, suggesting that urbanization and a more complex social environment may play a role in influencing brain size.
The incredible diversity and relatively rapid development of the known four hundred dog breeds make them a valuable resource for researchers interested in studying rapid changes within a species. One area of interest for scientists has been understanding the factors that contribute to brain size, as humans possess unusually large brains compared to their body size. Analyzing different dog breeds can help shed light on some of these questions.
Is there a correlation between brain size and the specific tasks for which a breed was bred? Are there differences in brain size between lap dogs and hunting dogs, for example? Or is brain size influenced more by life expectancy and the challenges associated with raising offspring? What is certain is that thinking and cognitive processes require a significant amount of energy, and maintaining a larger brain is energetically costly.
László Zsolt Garamszegi, an evolutionary biologist at the Ecological Research Centre in Hungary, has devoted considerable time to studying the evolution of brain size. He states that “domesticated animals may have brains up to twenty percent smaller than their wild ancestors. This is likely due to the fact that domesticated species lead simpler lives compared to their wild counterparts. In the safe environment provided by humans, there is no need to fear predator attacks or hunt for food. As a result, the energetically costly large brain is no longer necessary, and the freed-up energy can be allocated to other purposes, such as producing more offspring, which is crucial for domesticated animals.”
Niclas Kolm, from Stockholm University, focuses on brain evolution and the relationship between brain morphology variation and behavior. He suggests that “different dog breeds inhabit varying levels of social complexity and engage in complex tasks, which likely require a larger brain capacity. Therefore, we hypothesize that the selective pressures on the brain can differ among dog breeds based on the tasks they perform or their genetic distance from wolves.”
After several decades of preparation, the first comprehensive study on the brain size of different dog breeds has been conducted.
Tibor Csörgő, a senior research fellow at Eötvös Loránd University (ELTE), has been collecting skulls for many years. These skulls were subjected to CT scans performed by Medicopus Nonprofit Ltd. in Kaposvár.
Using the CT images, veterinarian Kálmán Czeibert reconstructed the brains and accurately measured their volumes. The invaluable collection of skulls was complemented by the Canine Brain and Tissue Bank, operated by ELTE for the past seven years. This allowed for the verification of brain volumes calculated from skull images using actual brains. In total, data was gathered from 865 individuals representing 159 dog breeds, with 48 specimens representing wolves.
The findings, published in the journal Evolution, reveal that wolves have an average brain volume of 131 cm3, associated with an average body weight of 31 kg. In dogs of a similar weight category, the brain volume is only about three-quarters of that, approximately 100 cm3.
These results confirm that domestication has led to a decrease in brain size in dogs. However, what surprised researchers is that the further a dog breed is genetically distant from wolves, the larger its relative brain size becomes. Interestingly, the original role of the breeds, average litter size, and life expectancy are unrelated to brain size.
According to Enikő Kubinyi, a senior research fellow at ELTE, the domestication of dogs began around twenty-five thousand years ago, but for ten thousand years, dogs and wolves did not differ significantly in appearance. It is only in the last two centuries, since the industrial revolution, that distinct-looking breeds have emerged due to the hobby-like nature of dog breeding. This transition to settlement, agriculture, pastoralism, and the accumulation of wealth brought about various tasks for dogs, such as guarding, herding, hunting, and companionship.
Kubinyi suggests that the breeding of modern dog breeds has been accompanied by an increase in brain size compared to ancient breeds. However, the reasons behind this change cannot be explained solely by the tasks or life history characteristics of the breeds. It is speculated that factors such as a more complex social environment, urbanization, and adaptation to societal rules and expectations may have contributed to this shift, influencing all modern breeds.
These findings align with previous research indicating that ancient breeds known for their independence show less attentiveness to human cues and bark less, exhibiting differences in visual and acoustic communication when compared to modern breeds.
Source: Eötvös Loránd University