Study Finds Modern Dog Breeds Have Grown Larger Brains Than Ancient Types — Why It Might Matter

Modern Dog Brains Are Growing — A Surprising Twist on Domestication

A new European study reports that many modern dog breeds have larger relative brain volumes than older, so-called ancient breeds, challenging simple assumptions about brain size and domestication.

What the Researchers Did

The international research team from Hungary and Sweden analyzed CT scans from more than 850 individual dogs representing 159 breeds to reconstruct brain volumes and compared those measurements with 48 wolf specimens. Using these data, they examined how brain size relates to body weight, breed history and genetic distance from wolves.

Key Findings

The study confirms earlier work showing that domesticated dogs generally have smaller brains than wolves: a dog of comparable body weight has roughly 75% of a wolf’s brain volume, consistent with a ~20% reduction linked to domestication. However, the surprising new pattern is that modern breeds that are genetically further from wolves tend to have relatively larger brains than breeds categorized as ancient.

“The breeding of modern dog breeds has been accompanied by an increase in brain size compared to ancient breeds,” says Enikó Kubinyi, Senior Research Fellow at the Department of Ethology, ELTE Institute of Biology.

What Didn’t Explain the Pattern

The authors tested several alternative explanations and found no relationship between relative brain size and functional category (for example, herding, guarding, or companionship), skull shape, lifespan, or litter size. In other words, traditional working roles and obvious life-history traits did not account for the increase.

Possible Explanations

The team offers hypotheses rather than definitive answers. One idea is that many modern breeds live in more socially complex, often urban environments that impose new behavioral expectations and rules, increasing cognitive demands. The researchers also point to behavioral differences between ancient and modern breeds—ancient breeds often bark less and respond less to human cues—as suggestive of different social sensitivity among groups.

“Perhaps the more complex social environment, urbanization, and adaptation to more rules and expectations have caused this change, affecting all modern breeds,” Kubinyi suggests. Niclas Kolm of Stockholm University adds that selective pressures on the brain likely vary within the species and that future work could link breed-specific tasks or genetic distance from wolves to brain differences.

Why It Matters

The finding complicates the neat narrative that domestication simply shrinks brains because energetic costs are reduced. Instead, it suggests that selective pressures since domestication have shifted in different directions for different breeds, possibly driven by human environments and social demands. The study highlights the value of combining imaging, comparative anatomy and genetics to understand how animals adapt to human-altered worlds.

Next Steps

The authors call for follow-up studies linking brain structure to behavior and cognition across breeds, and for genetic work to identify the evolutionary mechanisms underpinning the pattern.