New research suggests that current breeding efforts have led to a relative increase in dog brains compared to wolves, despite their smaller overall size. Over a century, the modern breeds of dogs’ skull size have grown larger than ancient breeds. However, the reason behind this change remains unknown.
Many studies stated that domestic animals, like dogs, cattle, sheep, fish, pigs, rabbits, and cats, generally have smaller brain sizes. This reduction in brain size is believed to be a response to a decreased need for cognitive abilities in terms of survival.
However, when scientists examined the skulls of 159 dog breeds, including wolves, they made an unexpected discovery. Although a wolf’s brain is 24 percent larger than that of a similarly sized dog, the brains of dogs grew more prominent as they genetically differed more from wolves.
This finding suggests that while the domestication of dogs long ago may have initially reduced certain parts of their brain related to mate choice, predators, or hunting, modern breeding practices have led to slight cognitive growth over the past 150 years.
Evolutionary biologist Niclas Kolm from Stockholm University in Sweden explains that dog breeds live in varying levels of social complexity and perform diverse tasks that likely require a larger brain capacity. However, the researchers’ hypothesis that dogs bred for more complex tasks like herding or sports would have larger relative brains was proven incorrect.
Instead, the study found that the only factor influencing the relative brain size of modern dog breeds was the genetic distance between the breeds and wolves rather than the function of the breed, litter size, or life expectancy. Furthermore, American Kennel Club has yet to identify any considerable difference among the breeds recognized by them.
While past research has indicated that an individual dog’s absolute brain size influences its memory and self-control, this does not appear to impact a breed’s overall relative brain size powerfully. Recent studies also support the notion that the behavior for which certain dogs are bred is not necessarily evident in their genetic makeup.
Ethologist Enikő Kubinyi from Eötvös Loránd University in Hungary speculates that the change in relative brain size among modern breeds may be attributed to factors such as the complex social environment, urbanization, and adaptation to societal rules and expectations.
It aligns with the social brain hypothesis, which proposes that larger brains can evolve to adapt to more complex social environments.
Previous research has indicated that dogs more closely related to wolves tend to have poorer communication skills than humans. To further understand the differences between ancient and modern dog brains compared to wolves, the researchers suggest future studies should examine the size of various brain regions. By doing so, scientists may unravel the impact of human influence on dog brains and behavior.