African wild dogs might use facial expressions to communicate with each other as they hunt in packs on the savanna. Arno Meintjes via Flickr under CC BY-NC-SA 2.0 DEED Puppy-dog eyes are irresistible.

Coyotes turn out to have face muscles that look capable of making that big-eyed, sad-puppy face that dogs have used to melt human hearts for eons. That discovery supports a rethink of humans’ history ...