Domestication leads to reduced brain size in dogs

The study conducted by László Zsolt Garamszegi and Niclas Kolm challenges the traditional belief that domestication is the primary factor leading to reduced brain size in domesticated animals, specifically dogs. The research aimed to determine if the reduction in brain size in domesticated dogs is a unique evolutionary trait or if it can be observed in a broader phylogenetic context among canid species.

The prevailing theory suggests that domestication results in a decrease in brain size due to reduced selection pressures for survival skills like foraging, mating competition, and predator avoidance. This reduction is believed to be a consequence of the decreased need for metabolically costly brain tissue in a domesticated environment. While domesticated dogs do exhibit a significant decrease in brain size compared to their wild ancestor, the grey wolf, this study sought to investigate whether this reduction is exceptional when compared to other canid species.

Garamszegi and Kolm analyzed brain and body size data for 25 canid species, including ancient dog breeds genetically closer to the ancestral domesticated dog. Their phylogenetic predictions and allometric regressions revealed that the reduction in brain size in domesticated dogs is not a unique evolutionary trait. The brain size of domesticated dogs fell within the expected range for most ancient breeds included in the study, indicating that domestication may not be the sole driver of brain size reduction among canids.

Interestingly, the study identified the common raccoon dog as a more pronounced outlier in terms of brain size reduction. This species, which hibernates, exhibited a significantly smaller brain size, suggesting that ecological adaptations like hibernation can also influence brain size evolution. The findings highlight that factors other than domestication, such as specific ecological adaptations, can play a significant role in driving reductions in brain size among species.

In conclusion, while domestication does play a role in reducing brain size in dogs, this study emphasizes that it should not be viewed as a uniquely powerful evolutionary force. The research suggests that other ecological and evolutionary pressures can similarly impact brain size and lead to extreme variations in non-domesticated species. A more balanced perspective that considers a range of factors beyond domestication could enhance our understanding of the complex relationship between brain size evolution and evolutionary processes in mammals. The work of Garamszegi and Kolm challenges existing notions and may reshape our understanding of the evolutionary impact of domestication on brain size.