Modern breeds of dogs that are more genetically distinct from wolves than ancient breeds that are thousands of years old and have relatively larger brains. This is the unexpected conclusion of a study by researchers from Hungary and Sweden that was decades in the undertaking. According to the researchers, the increase in brain size is not associated with the role of life history characteristics of the breeds in question. Instead, they believe that such has been influenced by urbanisation and introduction into a more complex social environment.
Paper author and evolutionary biologist Dr László Zsolt Garamszegi of the Ecological Research Centre in Hungary explained: “The brains of domesticated animals can be up to 20 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 to domesticated animals.”
The study undertaken by Dr Garamszegi and his colleagues is the first to take a comprehensive look at the brain sizes of different dog breeds — and took several decades to complete as the team collected skulls to analyse via CT scan.
Paper co-author and evolutionary biologist Professor Niclas Kolm of Stockholm University said: “Different dog breeds live in varying levels of social complexity and perform complex tasks, which likely require a larger brain capacity.
“Therefore, we hypothesised 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 takes they perform or their genetic distance from wolves.”
Based on the CT images, team member and veterinarian Dr Kálmán Czeibert reconstructed the brain sizes of each of the collected dog skulls, and determined the organs’ volumes.
His estimations were verified using data from the Canine Brain and Tissue Bank — a facility which the Eötvös Loránd University has been operating for the last seven years.
In total, the researchers accumulated data on 865 individual animals representing 159 dog breeds, alongside 48 specimens from wolves for the sake of comparison.
The researchers found that the wolves had an average brain volume of 20.3 square inches (131 cm²), associated with an average body weight of 68.3 lbs (31 kg).
Dogs in a similar weight category, in contrast, were found to have brain volumes around three-quarters the size, specifically around 15.5 square inches (100 cm²).
This finding, the team said, confirms that domestication has — as seen with other animals — led to dogs to undergo a decrease in brain size.
However, the researchers were also surprised to determine that the more genetically distinct a dog breed is from wolves, the larger its relative brain size becomes.
Moreover, brain size appears — contrary to the team’s expectations — to be independent of the original role of the breeds, their average litter size, or the animal’s life expectancy.
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Paper co-author and biologist Dr Enikő Kubinyi of the Eötvös Loránd University said “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.”
Humans, Dr Kubinyi explained, began to require guard dogs, herding dogs, hunting dogs, and even lap dogs.
He added: “However, a significant portion of the distinct-looking breeds known today has only emerged since the industrial revolution […] as dog breeding has become a kind of hobby.”
Dr Kubinyi continued: “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, urbanisation, and adaptation to more rules and expectations have caused this change, affecting all modern breeds.”
Such a conclusion appears to be supported by past studies that have found that ancient breeds known for their independence exhibit differences in communication — being less attentive to human cues, and barking less.
The full findings of the study were published in the journal Evolution.
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