A recent study has come to the conclusion that the domestication of the wolf reduced the brain size of dogs which is understandable because domestic dogs nearly always have everything done for them. They don’t need to face the challenges that wolves have to face. These challenges stimulate the mind and within the evolutionary process the brain becomes larger. And the reverse happens which is why domestic dogs have smaller brains than their wild ancestor the gray wolf.
The absolute brain size of wolves is more than 24% higher than that of dogs with the same body size – the study
More recent artificial selection of dog breeds and larger brains
However, this study also concluded that if the genetics of the dog breed concerned were more distant from the genetics of the wolf their brains became bigger. My interpretation is that these later or more modern breeds of dog created through selective breeding i.e. artificial selection over the past few hundred years resulted in the brain size becoming bigger because of the selective breeding process.
Interestingly, we identify a pattern of an increase in relative brain size with greater genetic distance from wolves – the study
My interpretation is that dog breeders would breed from foundation dogs that were perceived by them to be more intelligent than usual because they make better companions. This is not stated in the study as I understand it. It is my interpretation.
Two distinct forces
There are two forces involved dictating the brain size of dog breeds. Those that are ancient dog breeds, closer genetically to their wild ancestor, the wolf, which have smaller brains than the wolf because of up to 20,000 years of pampered domestication.
The other force involved counteracts this in terms of brain size. This is the effect of selective breeding in selecting the more intelligent breeding dogs. The reason why I have stated this is because the scientists did not know why these more modern dog breeds are evolving with bigger brains. I presume by the way that even though the brains are bigger than the ancient dog breeds they are still smaller than those of the wolf.
Interactivity is important
It seems like common sense to me that modern breeds will have bigger brains because people want dogs to be interactive. The interactivity of a dog comes from their intelligence. The desire to be stimulated and their desire to be active and involved with their human companion.
Although, there would appear to be a negative in that argument because the border collie is known to be perhaps the most intelligent dog breed but they are also said to be quite difficult to live with because they need constant stimulation and activity.
Perhaps there is an optimum level of dog intelligence based upon brain size. This would be a dog that is not too intelligent to the point where they become challenging to the human caregiver. These are personal thoughts. Comments are welcome as usual.
Evolution of relative brain size in dogs—no effects of selection for breed function, litter size, or longevity. Authors: László Zsolt Garamszegi, Enikő Kubinyi, Kálmán Czeibert, Gergely Nagy, Tibor Csörgő, Niclas Kolm. Link: https://doi.org/10.1093/evolut/qpad063. Date: 18 April 2023.