We were recently alerted to the Nova documentary, “Dogs Decoded,” so of course we had to check it out. And are we glad we did! The film is chock full of information on both the evolution of dogs, and how dogs have come to relate and interact with humans in a manner unlike any other pairing of species. We highly encourage you to check out the show, which is available to stream online via Amazon Instant Video. Until you get the chance to watch it, here are some highlights to tide you over:

• There are more pet dogs than babies in this world, at nearly half a billion

• Daniel Mills (Professor of Veterinary Behavioural Medicine, University of Lincoln, England) has used eye tracking software on dogs to prove that they do, in fact, read human faces in the same manner that humans do, i.e., with a left-to-right gaze (meaning that they view the right side of the face first). Research has shown that human facial expressions are not symmetrical and manifest differently on each side of the face, and that the right sight is usually the truest to that emotion. Dogs appear to have figured this out all on their own.

• Mills speculates that dogs have evolved to read human emotion, as there may be a biological advantage to it for them, living as closely with humans as they do. If they can recognize the expressions a human displays when (s)he is acting aggressively, the dog will know to avoid the human when they are displaying those emotions in the future. The converse is also true; when a human is displaying pleasant or happy expressions, the dog knows that it is safe to approach, and that affection is likely.

• It is theorized that dogs actually developed their current vocal repertoire expressly to communicate with us. Dog’s relatives/ancestors, the wolves, only bark as a means of expressing a warning; they do not bark to communicate anything else. So what other reason could there be for dogs to develop a more extensive range of vocalizations?

• Research by Swedish scientist Kerstin Uvnäs-Moberg (Karolinska Institute, Sweden) has shown that humans and dogs have a biochemical response to each other. Blood draws from each species during petting sessions showed spikes in the levels of oxytocin present in the bloodstream at 1 and 3 minutes in, where no oxytocin was present prior. Oxytocin is the hormone responsible for the immediate bonding experience between a mother and her child, and also plays a role in the mediation and mitigation of stress.

• Greger Larson (Durham University, England) believes that domestication of dogs was the crucial step that allowed our civilization to thrive and evolve. According to Larson, dogs allowed us to take down large game, making us better hunters. Large game meant more food, which meant healthier people, which ultimately led to more people, which led to civilization. Without dogs, Larson believes, we’d still be hunter-gatherers.

• Experiments by Juliane Kaminski (Max Planck Institute, Germany) showed that dogs are so tuned into our social cues that they can even pick up on something as subtle as the direction of our gaze. These are skills dogs don’t use in communication with each other; they only use them to communicate with us. Essentially, they had to learn a second language to communicate with us. This starts as early as 6 weeks of age.

• Some dogs have even learned to recognize objects by name, such as Betsy, the border collie, who has a vocabulary of over 350 words – rivaling that of a 2 year-old. Betsy can even identify a 3D object from a 2D picture of it.