Dogs’ facial fast twitch muscles provides them with expressions which entice us

Doe-eyed dog
Doe-eyed dog. Image by Pexels from Pixabay

Unlike domestic cats, domestic dogs have a face-full of fast twitch muscles which enable them to have expressive faces and rapid barks. Their bark is entirely different to that of their wild ancestor the wolf.

Wolf bark compared to the domestic dog bark

And it is postulated that this evolution of facial muscles has been brought about in two ways. Firstly, when the wolf self-domesticated they, through involuntary but evolutionary selective breeding, developed facial muscles because they provided domesticated wolves with the means to better communicate with their early human caregivers. In doing so they received more of what they desired. This is right at the beginning of dog domestication.

And secondly, a large percentage of domestic dogs are purebred. And purebred dogs are selectively bred. This is artificial selection by dog breeders to create companion animals that look like the breed standard and which have a character making them good companions. One issue is that breeders have gone too far on occasion and bred unhealthy animals e.g., French bulldog.

Through artificial selection, breeders have gradually bred into these dogs an anatomy which includes fast-twitch facial muscles, particularly around the eyes, which results in those expressive, enticing eyes which beguile their owners.

So, the adoring mournful expression in your dog’s eyes has evolved over about 25,000 years of domestication. We don’t know, exactly, for how long the dog has been domesticated but it is perhaps two or three times longer than the domestic cat. This may be one reason why cats have such impassive faces. It takes time for anatomy to evolve. It’s believed that dogs were first domesticated in Palaeolithic times (2.6 million years ago to about 12,000 years ago). Wolves approached human settlements for scraps of food and the process of domestication took off from there. It was a mutual agreement much like the domestication of the cat.

Domestic cats do have facial expressions but they are very subtle and nowhere near those in terms of sophistication of the dog. Cats have fast twitch muscles too but they are in their legs!

About three years ago researchers uncovered a specific muscle which had evolved around the eyes of dogs which allow them to raise their eyebrows in that well-known irresistible way.

Do dogs show remorse?

A more recent scientific study has augmented those early findings and allowing us to better understand the plethora of muscle differences between domestic dogs and wolves. They conclude that the eyes of dogs have been humanised and their ability to scare off wild animals by howling has been selectively bred out of them.

Wolves don’t have facial expressions like domestic dogs. The lead author of the research is Anne Burrows of Duquesne University in Pittsburgh. They decided that the domestic dog can show emotions better than any other animal other than the human being. Through their facial expressions dogs are able to communicate with us. They can grab our attention which I guess is part of their requesting process.

Fast-twitch muscles are better able to contract more rapidly which allows for expressive facial expressions. It also allows for rapid barks. They found that modern dogs have nearly all fast twitch muscles and “hardly any slow twitch fibres at all”, said Burrows.

There are some more pages on evolution below.

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