Companion Animals

How puppy dog eyes evolved

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Science  12 Jul 2019:
Vol. 365, Issue 6449, pp. 136-137
DOI: 10.1126/science.365.6449.136-g

Humans selected for dogs' expressive eyebrows.

PHOTO: SARAH BICKEL

Dogs are adorable. We are often amazed at just how humanlike their facial expressions can be when they gaze into our eyes. Kaminski et al. provide an evolutionary explanation for how “puppy dog eyes” came to be, by comparing the facial muscles of dogs with their closest living relatives, wolves. As dogs became domesticated thousands of years ago and began to form bonds with humans, both their anatomy and behavior developed as a result of selection for favorable traits. Dogs (but not wolves) harbor the levator anguli oculi medialis muscle, which is responsible for raising the inner eyebrow. This allows dogs to produce eyebrow movements that are more frequent and expressive than those of wolves, in turn giving dogs an evolutionary advantage with humans, who instinctively respond more positively.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1820653116 (2019).

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