Dogs' Brains Began Shrinking 5,000 Years Ago, Study Shows

A new analysis of canine skulls shows dogs’ brains began shrinking at least 5,000 years ago. Late Neolithic dogs (?5,000–4,500 BP) had brains 46 % smaller than contemporary wolves, similar to modern pugs. Modern dogs, dingoes and village dogs have brains about 32 % smaller than ancient and modern wolves.

The Guardian

Genetic evidence places domestic dogs 15,000 years ago; scholars dispute when brain-size reduction began; researchers at French National Centre for Scientific Research scanned 22 canids (35,000–5,000 years) and compared them with CT scans of 59 wolves and 104 dogs, including breeds, village dogs, dingoes, using cranial volume as brain-size proxy.

The Guardian

• Modern dogs, dingoes, village dogs: 32 % smaller brains than wolves.

The Guardian

• Late Neolithic dogs: 46 % smaller brains than contemporary wolves, body-size adjusted.

The Guardian

• Two protodogs (35,000 yr and 15,000 yr) showed no reduction; one had a relatively larger brain.

The Guardian

Authors propose that reduced brain volume reorganized circuitry, making dogs less trainable but more vigilant—traits useful as “alarm systems.” Neolithic food may have favored smaller brains, and stress that smaller brains do not imply reduced intelligence. Dr Thomas Cucchi, author, emphasized dogs remain “extremely clever” and adept at reading humans. Dr Juliane Kaminski of University of Portsmouth noted protodogs lacked brain-size hallmark, suggesting syndrome emerged later than genetic evidence indicates.

The Guardian

Some scholars argue brain-size reduction reflects recent breed specialization over the past 200 years rather than a universal domestication marker. Protodog data conflict with expectations that shrinkage began early, leaving the timing of the full domestication syndrome uncertain. The study does not explain quirks such as dogs’ preference for muddy water.

The Guardian

• “The way our dogs live nowadays doesn’t give them the opportunity to always express most of their intelligence,” — Dr Thomas Cucchi, French National Centre for Scientific Research

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• “But they are extremely clever and domestication didn’t make them stupid, but made them really capable of reading us and communicating with us.” — Dr Thomas Cucchi, French National Centre for Scientific Research

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• “They didn’t yet show this sign of domestication that we thought is [a] standard part of this domestication syndrome,” — Dr Juliane Kaminski, University of Portsmouth

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• “What [the authors] are simply saying is: OK, the timeline of the full domestication syndrome being in place is maybe a little bit later than the genetic data suggests,” — Dr Juliane Kaminski, University of Portsmouth

The Guardian

The team plans to expand fossil scanning to map brain reorganization and to test energy-budget models that could explain selective pressure for smaller brains in early village dogs.

The Guardian