Man’s best friend

Aster E. Pijning
Sep 5, 2018 · 4 min read

The co-evolution of Canis familiaris and Homo sapiens

“white and black dog with leash sitting on snowfield at daytime” by James Padolsey on Unsplash

Compared to all other species on or planet, dogs really are our very best friends. We care as much for our four-legged fur ball as we do for our own flesh and blood. The day Sparky the Golden Retriever dies is the saddest day in many a child’s life. And I have heard of people choosing their German Shepherd over their allergic partner in a joking-but-not-really-joking kind of way.

We depend on our dogs to give us enjoyment, distraction, and above all to love us as unapologetically and unconditionally as we wished our lovers did. The ownership of a dog has even been linked to beneficial health outcomes, including a reduced risk of Alzheimer’s disease and increased immune function.

Have you ever wondered where this deep and universal connection to dogs comes from? How about an astonishing 30.000 years of co-evolution.

Man have roamed with dogs for longer than any other animal, including cattle and horses. It is thought that the wolves who are the ancestors of the C. familiaris initially started following packs of humans around to feed of their discarded food. Most people think that at this point, the humans took a liking to these furry animals and the rest is history. But that’s not exactly how things went down.

The humans back then were not usually inclined to share their food or even tolerate competing hunters. In fact, whenever H. sapiens arrived in new territory, the first thing they did was drive to extinction any and all species competing for food. So why then, was an exception made for the wolf?

One theory suggests that we may have had an unintentional but dramatic effect on the evolution of the wolf. Of the wolf packs that lurked around groups of humans, those animals that were aggressive towards people would be the first to go. This would lead to the friendlier wolves surviving and having more offspring, gradually becoming a friendlier species. It would have also been in the best interest of the wolves to read and understand human behaviour as best as possible. Which is why nowadays, dogs are able to understand our movements and intentions better than chimpanzees can.

After their initial inauguration as a domesticated species, dogs became invaluable to human hunter gatherers. They were used to aid in the hunt, for protection of the young and helpless, and as back-up food supply if times were tough. Theirs and our co-evolution continued. There is a theory about how these newly domesticated wild animals, not far removed from their wolf ancestors, turned into the happy docile creatures we know today.

William-Beurens syndrome is a genetic defect that occurs in about 1 in 10,000 people and causes intellectual disability. The syndrome is causes by the deletion of a rather large chunk of the genome, encompassing 27 genes. People affected with this condition are known to be exceptionally social and keen on human interaction. In 2010, researchers looking into the differences between wolf and dog genomes, stumbled upon 3 genes that were important in the domestication of dogs, and that could predict behavioral differences between wolves and dogs. All three genes are located in the area affected in William-Beurens syndrome. A deletion of two of these genes was already shown to result in extremely social behavior in mice.

In short, a theory amongst evolutionary biologists is that a mutation in one or multiple genes gave rise to a generation of docile and friendly wolf/dogs. Where these traits would have usually been detrimental to their survival, and thus out-competed, since dogs were already semi-incorporated into human life they could remain and prosper. Since the full domestication of dogs, big evolutionary events have been connected between the two species. Similar adaptations in metabolism occurred in response to changes in diet in both species. Alterations in the way the neurotransmitter serotonin is processed would lead to reduced levels of aggressive behaviour of both man and canine kind.


A relationship forged by the passing of a lot of time, some mutations, and luck. Nowadays many domesticated dogs have become completely reliant on us. I for one, would love to see a show about a group of Chihuahuas and Pomeranians being set free in a forest to play out a Hunger Games type of scenario. However, PETA will most likely not find this as amusing. Over a relatively short amount of time, we have selected dogs on both physical and behavioural characteristics to the extent where many of the current ‘purebred’ (inbred) breeds would not be able to survive without human help. Golden retrievers are often not able to give birth without the aid of a caesarian section, because their hips have become too narrow for pups to pass. Other breeds, like the Cavalier King Charles Spaniel, live in constant pain because of the generations of inbreeding we have subjected them to.

So it would seem that our once mutualistic relationship has become a rather toxic one, with one species dominating and controlling the other. However one feels about this, fact is that the evolution of both our kinds, dogs and man, are linked. We have co-evolved to a point of no return.


VonHoldt et al. Nature. 464(7290):898–902. doi: 10.1038/nature08837 (2010).

Biology of Life

The Biology of Daily Life, Explained.

Aster E. Pijning

Written by

A molecular biologist with a short attention span.

Biology of Life

The Biology of Daily Life, Explained.

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