Scientists have figured out when dogs' brains started to shrink

Important: this does not mean that the dogs are "dumbed down". Scientists emphasise that a shrinking brain does not equal a decrease in intelligence, and that domestication has made dogs particularly able to understand and communicate with people.

Details

The researchers studied CT scans of the skulls of 22 ancient wolves and dogs between 35,000 and 5,000 years old, as well as 59 modern wolves and 104 modern dogs. The sample included various modern breeds, village dogs and dingoes.

Since the brain is not preserved in archaeological finds, the scientists used digital models of the inside of the skull cavity - so-called endocasts. These can be used to estimate the volume of the brain that once occupied this space.

The results showed that modern dogs, dingoes, village dogs and Late Neolithic dogs generally had brains about 32 per cent smaller than ancient and modern wolves. The difference was particularly marked in Late Neolithic dogs, which lived about 5000 - 4500 years ago: their brains were about 46 per cent smaller than those of wolves from the same period.

Meanwhile, earlier animals that lived alongside humans 35,000 and 15,000 years ago and are sometimes referred to as "proto-dogs" did not show such a brain reduction compared to ancient wolves. One of these earlier specimens, on the other hand, may have had a relatively larger brain.

Why it matters

The study changes the idea of when dogs showed some signs of full domestication. Previously, brain shrinkage was often attributed to the very beginning of domestication, but the new findings indicate that this process may have taken shape much later.

One possible reason is living near agricultural settlements. In such an environment, dogs may have benefited from other qualities: alertness, reaction to unfamiliar stimuli, barking as a warning of danger, the ability to live near people and to feed on available resources. The researchers also concede that a smaller brain could have been advantageous energetically because it requires fewer resources.

But that doesn't mean the dogs became less intelligent. Rather, their brains and behaviours changed to suit new challenges: not survival in a wolf pack, but living close to humans.

Background

Dogs were domesticated from wolves at least 15,000 years ago, but the details of this process are still debated. Some traits may have appeared early, others much later, when the human-dog relationship became closer.

The authors and independent experts believe it is significant that early "proto-dogs" did not yet show brain shrinkage. This could mean that the human-dog bond was looser at first, with the full set of domestication traits forming later.

Source

The study is published in Royal Society Open Science in 2026: Brain size reduction in dogs was already established at least by the Late Neolithic of western Europe, 5,000 years ago. The work used CT scans of ancient and modern dog and wolf skulls to trace changes in brain volume in the wolf-dog lineage.