A new analysis of prehistoric skulls finds that dogs underwent a dramatic and abrupt reduction in brain size during the Late Neolithic, at least 5,000 years ago. The shift coincided with the rise of sedentary human communities and the transition to farming. By the end of this period, dog brains were roughly comparable in volume to those of today’s small terrier and dwarf breeds, similar to modern pugs. The study appeared in Royal Society Open Science.
Researchers used endocranial volume measurements from CT scans of wolf and dog skulls dated between 35,000 and 5,000 years old. They report a reduction of approximately 32% to 46% relative to ancient and modern wolves. This marked a shift in canine biology that aligns with domestication syndrome, in which anatomical changes track with altered selection pressures under human care. The findings point to a “biological economy” favoring a smaller, more energy-efficient brain where food and protection were more secure and where social and communication skills with humans were advantageous.
The Late Neolithic emerges as a turning point in dog cognition and anatomy, according to Der Standard. Earlier ancestral dogs appear to have maintained brain sizes similar to their wolf relatives. Some specimens living alongside humans between 35,000 and 15,000 years ago did not show a reduction compared to ancient wolves, and at least one individual had a relatively larger brain volume. The data suggest an initial increase during the earliest phases of domestication, followed by a later contraction as dogs adapted to human-dominated, agrarian settings.
By around 5,000 years ago, dog brain size had converged toward that of small terrier and dwarf breeds. This indicates the major reconfiguration occurred well after the first steps toward domestication. Spanning tens of thousands of years, the study underscores that the reduction did not unfold gradually from the origin of domestication but happened decisively in the Late Neolithic.
The timing aligns with permanent settlements, more reliable food provisioning, and shifts in human-animal relationships. In these contexts, strict natural selection pressures tied to survival in the wild eased, allowing dogs to reallocate biological resources. A smaller, metabolically cheaper brain could accompany specialization in social cognition and communicative abilities suited to human environments. In domesticated species broadly, a 20% to 30% brain-size decrease is often cited as a marker of domestication, and the dog’s 32% to 46% contraction fits within and even exceeds that range.
The shift in brain volume is framed as an adaptation to a niche emphasizing cooperation, understanding, and communication with people. Researchers note that modern dogs may not always have daily opportunities to show their full intelligence, and cranial evidence points to enhanced responsiveness to human cues rather than diminished cognition.
Source:
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