Dog lovers are well aware of the ability of a dog to communicate with its eyes. Now, scientific research suggests this ability developed over time as dogs learned to live with humans. Just like humans, the eyes can be one of the most appealing things about dogs, the animals known in many cultures as “man’s best friend.” But a new study found evidence that dogs developed in physical ways to present “puppy dog eyes” as a way to help connect with humans. Researchers in Britain and the United States did the study. Results were published in the Proceedings of the National Academy of Sciences. The study compared the facial muscles of dogs and wolves, which share ancestral history. Dogs broke off from wolves after being domesticated about 33,000 years ago. During that time, dogs changed physically and behaviorally to fit life with humans.