Puppy Eyes? Researchers thank evolution.

Apparently, dogs evolved a special muscle to show those puppy eyes.

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According to the New Scientist, dogs evolved a muscle that allows for expressive faces thanks to Human selection. Apparently, they can lift an inner "eyebrow" that makes their eyes seem larger and their faces sad. Researchers seem to think this evolution is a result of people favoriting dogs that could make this expression.

+ New Scientist