close
Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2019 Jul 16;116(29):14677-14681.
doi: 10.1073/pnas.1820653116. Epub 2019 Jun 17.

Evolution of facial muscle anatomy in dogs

Juliane Kaminski  1 , Bridget M Waller  2 , Rui Diogo  3 , Adam Hartstone-Rose  4 , Anne M Burrows  5
Affiliations

Evolution of facial muscle anatomy in dogs

Juliane Kaminski et al. Proc Natl Acad Sci U S A. .

Abstract

Domestication shaped wolves into dogs and transformed both their behavior and their anatomy. Here we show that, in only 33,000 y, domestication transformed the facial muscle anatomy of dogs specifically for facial communication with humans. Based on dissections of dog and wolf heads, we show that the levator anguli oculi medialis, a muscle responsible for raising the inner eyebrow intensely, is uniformly present in dogs but not in wolves. Behavioral data, collected from dogs and wolves, show that dogs produce the eyebrow movement significantly more often and with higher intensity than wolves do, with highest-intensity movements produced exclusively by dogs. Interestingly, this movement increases paedomorphism and resembles an expression that humans produce when sad, so its production in dogs may trigger a nurturing response in humans. We hypothesize that dogs with expressive eyebrows had a selection advantage and that "puppy dog eyes" are the result of selection based on humans' preferences.

Keywords: domestic dogs; domestication; facial muscle anatomy; wolves.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Facial musculature in the wolf (C. lupus) (animal’s left) and dog (C. familiaris) (right) with differences in anatomy highlighted in red. Image courtesy of Tim D. Smith (Cambridge University Press, Cambridge, UK).
Fig. 2.
Fig. 2.
Right-side facial masks from domestic dog (C. familiaris) and gray wolf (C. lupus). B, buccinator muscle; C, caninus muscle; DS, depressor septi muscle; F, frontalis muscle; LLM, levator labii maxillaris (deep to LN); LN, levator nasolabialis muscle; M, mentalis muscle; OOc, orbicularis oculi muscle; OOM, orbicularis oris muscle; P, platysma muscle (note that this muscle is cut away in the gray wolf to reveal the SCP); SCP, sphincter coli profundus muscle; Z, zygomaticus muscle. Green line encircles the LAOM in the domestic dog and the typically reduced LAOM in the gray wolf. Terminology based on ref. .
See this image and copyright information in PMC

Comment in

  • Domesticated species: It takes one to know one.
    Raghanti MA. Raghanti MA. Proc Natl Acad Sci U S A. 2019 Jul 16;116(29):14401-14403. doi: 10.1073/pnas.1908964116. Epub 2019 Jun 20. Proc Natl Acad Sci U S A. 2019. PMID: 31221753 Free PMC article. No abstract available.

References

    1. Thalmann O., et al. , Complete mitochondrial genomes of ancient canids suggest a European origin of domestic dogs. Science 342, 871–874 (2013). - PubMed
    1. Coppinger R., Coppinger L., Dogs: A Startling New Understanding of Canine Origin, Behavior and Evolution (Scribner, New York, 2001).
    1. Hare B., Brown M., Williamson C., Tomasello M., The domestication of social cognition in dogs. Science 298, 1634–1636 (2002). - PubMed
    1. Kaminski J., Marshall-Pescini S., The Social Dog: Behavior and Cognition (Elsevier, 2014).
    1. Marshall-Pescini S., Kaminski J., The Social Dog: History and Evolution (Academic, 2014).

LinkOut - more resources