For this there is also a theory of antiquity. The anatomy of the primitive dogs, descendants of the wolves, was very different from what we know today, they were less expressive than the current ones, for a simple reason: there was no development of the muscles of their eyebrows. Now, with a simple glance we know what our beloved dogs want.
The tender face they give you when you are eating and they want your food is an expression that the first domesticated dogs did not have. The movement of their eyebrows evolved over time and has allowed us to understand each other better.
Scientists believe they have understood how dogs do to soften people and thus gain their affection: two muscles around their eyes help them to look sad, a technique mastered by human babies.
That is, part of its evolution, were attitudes learned after living 30 thousand years with humans, the species has managed to incorporate cognitive skills to better communicate with us. For research they were compared to wolves.