Biotechnology

The brains of modern dog breeds are larger than those of ancient breeds

[ad_1]

Modern dog breeds that are genetically more distant from wolves have relatively larger brain sizes compared to ancient dog breeds that are thousands of years old, Hungarian and Swedish researchers have found. The increase in brain size could not be attributed to any role or life history characteristics of the breed, suggesting that it was likely influenced by urbanization and a more complex social environment.

Modern dog breeds that are genetically more distant from wolves have relatively larger brain sizes compared to ancient dog breeds that are thousands of years old, Hungarian and Swedish researchers have found. The increase in brain size could not be attributed to any role or life history characteristics of the breed, suggesting that it was likely influenced by urbanization and a more complex social environment.

Even today, the four hundred known dog breeds have evolved relatively quickly and exhibit great diversity, making them a treasure trove for researchers interested in rapid changes within a species. Scientists have long been curious about the factors that affect brain size because the human brain is very large compared to body size. Comparing different breeds of dogs can help answer some questions.

Is there a correlation between brain size and the specific task with which it is bred? Is there a difference, for example, between a lap dog and a hunting dog? Or are you more influenced by life expectancy and the challenges of raising children? What we know for sure is that

thinking and cognitive processes require a lot of energy, and maintaining a larger brain is expensive.

Ladislaus Zsolt Garamszegi, an evolutionary biologist at the Center for Ecological Research in Hungary, has long studied the evolution of brain size. “Pets’ brains can be up to twenty percent smaller than the brains of their wild ancestors. The probable reason for this is that the life of the domesticated species is simpler compared to that of the wild species. In the safe environment provided by humans, there is no need to fear predator attacks or hunting for food. Therefore, there is no need to maintain a cerebrum which consumes a lot of energy, and the freed energy can be directed towards other goals, such as producing more offspring, which is important for pets.”

Niclas Colm, at Stockholm University, focuses on the evolution of the brain and the relationship between variations in brain morphology and behavior. “Different dog breeds live in varying degrees of social complexity and perform complex tasks, which likely require greater brain capacity. Therefore, we hypothesize that selective pressure on the brain may vary within canine species, and we may find differences in brain size between breeds based on the tasks they perform or their genetic distance from wolves.”

This is the first comprehensive study of the brain size of various dog breeds, and it took decades to prepare.

Tibor Csörgő, a senior researcher in the Department of Anatomy, Cell and Developmental Biology at Eötvös Loránd University (ELTE), has been collecting skulls for decades. CT scan of the skull was performed by Medicopus Nonprofit Ltd. in Kaposvár.

Based on the CT images, the vet Kálmán Czeibert reconstruct the brain and determine its exact volume. This priceless collection is complemented by the Canine Brain and Tissue Bank, operated by ELTE for the past seven years, which allows verification of brain volume calculated from skull images using actual brains. In the end, data was collected from 865 individuals representing 159 dog breeds, with 48 specimens representing wolves.

According to the results published in the journal Evolution, wolves have an average brain volume of 131 cm3, related to an average body weight of 31 kg. In the case of dogs of the same weight category, the brain volume is only about three-quarters that, approximately 100 cm3. This confirms that domestication also led to a decrease in brain size in dogs. However, what surprised the researchers was that the further genetically distant dog breeds were from wolves, the larger their relative brain size. Contrary to expectations, breed origin, mean litter size, and life expectancy were independent of brain size.

“Domestication of dogs began approximately twenty-five thousand years ago, but for ten thousand years, the appearance of dogs and wolves was not that different. Many ancient breeds, such as sled dogs, still resemble wolves today. However, transitions to settlement, farming, grazing, and wealth accumulation offer a variety of tasks for dogs, requiring guard dogs, herding dogs, hunting dogs, and even lap dogs. However, most of the distinct looking breeds known today have only appeared since the industrial revolution, especially in the last two centuries, as dog breeding has become something of a hobby,” said Eniko Kubinyia senior researcher in the Department of Ethology at ELTE.

“The results show that the proliferation of modern dog breeds was accompanied by an increase in brain size compared to ancient breeds. We cannot explain this in terms of task or breed life history characteristics, so we can only speculate about the reasons. Perhaps a more complex social environment, urbanization and adaptation to more rules and expectations have led to these changes, affecting all modern races.”

These findings are supported by research showing that ancient breeds known for their independence paid less attention to human cues and barked less, displaying differences in visual and acoustic communication compared to modern breeds.


Original publication: László Zsolt Garamszegi, Enikő Kubinyi, Kálmán Czeibert, Gergely Nagy, Tibor Csörgő, Niclas Kolm, Evolution of relative brain size in dogs – no selection effect for breed function, litter size or longevity, Evolution, 2023, qpad063, https:// doi.org/10.1093/evolut/qpad063

Funding: This study was supported by the Hungarian Academy of Sciences through a grant to the Hungarian Academy of Sciences (grant no. PH1404/21) and the National Brain Program 3.0 (NAP2022-I-3/2022), and by the National Research, Development and Innovation Office ( grant no. 2019-2.1.11-TET-2020-00109) and the Swedish Research Council (grant no. 2021-04476).


[ad_2]

Source link

Related Articles

Back to top button