Science is making it very clear: dogs have spent tens of thousands of years evolving so they can play humans like suckers. This article in Live Science lays it all out.

If you were to be face to face with a wolf you’d be able to make out SOME of its physical cues. “Teeth bared” and “snarling” clearly indicate that it is feeling threatened or wants to eat your face. But you wouldn’t get much of a read when it came to more subtle wolf emotions. The reason: wolves don’t have eyebrows. OK, they have eyebrows but their eyebrows are very, very different than their cousins the canis familiaris or “doggos”. This article from New Scientist explains how, over thousands of years, dogs developed muscles that wolves don’t have. They adapted eyebrows are what allow your pooch to manipulate you emotionally. “Puppy Dog Eyes” are actually an evolutionary adaptation.

Check out this “ashamed dog” video (there are about 20 quintillion of them on YouTube).

EVERYTHING that dog is doing is part of it’s species’ survival strategy. The sorrowful eyes, the bowed head, the sideways glances…they’re all adaptations to human behavior. The dog may not KNOW that it’s eyes look “sorry” to us. This is done through the awesome power of “natural selection” (and yes, I say “natural selection” since we humans are part of the natural world, especially 30 thousand years ago). Say a caveman…we’ll call him Ogg…has some leftover meat from his most recent hunt. He’s still hungry and is thinking about eating it. Then he notices his wolf/proto-dog companion looking up at him. Which wolve/dog would be more likely to get the food? One who had evolved the muscles for making sad eyes or one that hadn’t? It’s safe to say the animal who could trigger human emotion by mimicking our own emotions would be more likely to to feed, ergo to suvive, ergo to pass on his or her genes to offspring. And that is the basics of natural selection and evolution.

We’re able to recognize facial expressions in apes, our closest relatives in the animal kingdom. That’s because we only split off with them a few million years ago. We split off from the branch that would become wolves and dogs several TENS of millions of years ago. We share some of the same expressions with apes because of our close relationships. Dogs have basically “learned” that in only 30,000 years. That’s an astonishingly short amount of time of the evolutionary scale.

Check out your cat. You can pick up on some of what your cat is feeling (99% of the time it’s, “give me food”). But your cat doesn’t emote with its eyes the same way your dog does. Cat’s don’t have the same facial expressions as our dogs do because they never evolved those muscles.

That’s not to say that cats haven’t evolved to manipulate humans. Scientists have observed that cats don’t “meow” around other cats. They only do it when a human is around. Scientists think they may have evolved to make this sound because it kind of sounds like a human baby in distress. Cool, huh?