Scientists have determined that approximately 5,000 years ago, the volume of dog brains unexpectedly began to decrease. This phenomenon remains a mystery for researchers, as the changes occurred long before active interactions between animals and humans.
This is reported by Finway
Archaeological Findings and Skull Analysis
A scientific team led by Dr. Thomas Kukki from the French National Centre for Scientific Research (CNRS) conducted an analysis of dog skulls from a settlement on the shores of Lake Chalain (eastern France). The studied skulls preserved the shape of the internal cavity, allowing scientists to estimate the brain volume of ancient dogs. It turned out that their brain volume was significantly smaller than that of local wolves — the difference reached about 46%. Researchers emphasize that such a large difference cannot be explained solely by the body size of the animals. Moreover, this phenomenon is observed in several individuals from this settlement, indicating a systematic change.
“The analysis results show that these ancient dogs had a smaller brain volume from the very beginning compared to the nearby wolves, with differences reaching about 46%. Scientists argue that this difference is too great to be explained solely by body size. Furthermore, the difference is consistent across several individuals from this settlement. Such a pronounced reduction suggests that conditions in a settled human environment were a driving force — leaving open the question of what specific factors led to this change.”
Environmental Influence and Evolutionary Changes
Researchers also analyzed the skulls of other ancient animals: a 35,000-year-old dog from the Goyet Cave (Belgium) and a 15,000-year-old one from Bom-Trokada (southern France). None of them exhibited the brain shrinkage that could have resulted from the initial close contact between wolves and humans. One of the skulls even had a relatively larger brain volume, complicating the overall picture of dog evolution.
The changes are evidently linked to the emergence of agricultural settlements. In Chalain, dog skulls were found alongside household waste rather than in special burials, indicating their place in ordinary rural life. Analysis showed that the sizes of the animals did not exceed those of modern decorative breeds, such as small terriers. Researchers suggest that the villagers deliberately bred dogs, similar to modern owners, although selection was already occurring before the formal emergence of breeds.
According to the authors, the reduction in brain volume could have practical significance: brain tissue consumes a lot of energy, so reducing its volume might have helped the animals survive in conditions of limited resources.
Moreover, brain volume affects behavior: its reduction can change the balance between flexibility of thought and speed of reaction. However, scientists emphasize that this does not mean that ancient dogs were “unsuccessful wolves.”
Although today researchers have a clearer understanding of the stages of change, the reason for the reduction of brain size in dogs remains a subject of scientific debate.