Evolution of facial muscle anatomy in dogs.
Level 5 - mechanism / opinion, no new human data
Animal anatomical and behavioral comparative study
PubMed 31209036 · doi:10.1073/pnas.1820653116
What was done
Researchers examined facial anatomy through head dissections of dogs and wolves, specifically assessing the presence of the levator anguli oculi medialis muscle responsible for raising the inner eyebrow. They also collected behavioral observation data on eyebrow movement frequency and intensity in both dogs and wolves.
What was found
The levator anguli oculi medialis muscle was uniformly present in dogs but not in wolves. Dogs produced the inner eyebrow movement significantly more often and with higher intensity than wolves did, with the highest-intensity movements produced exclusively by dogs. The abstract reports no exact counts, percentages, sample sizes, or test statistics.
Why it matters
These findings suggest that artificial selection during domestication altered canine facial musculature within 33,000 years to facilitate human-like facial communication and potentially trigger human nurturing responses.
Limits
The abstract reports no sample sizes for either the anatomical dissections or behavioral observations. It does not provide numerical data, variance, or details on dog breeds, wolf subspecies, or animal rearing conditions.
Cited by
- contradicts Great apes have facial musculature and control similar to humans, whereas monkeys and dogs lack the musculature to produce those types of facial expressions.