The Essence Of Dogginess

by Malcolm Riordan

We all have our understanding that a dog's personality and behavior stem from the genetics they inherit and the shaping of their early life experiences. Dogs, like people, are a product of heredity and environment.

Looking at the group of domesticated animals, most of us would agree that our dogs - with 11,000 years (the longest period of domestication) - are the closest, most familiar, and most advanced of the domesticated species.

In the mid-1800s Darwin had noted with curiosity that floppy ears were a characteristic that could appear in each of the domesticated species. Darwin and naturalists since collectively came to recognize Domestication Syndrome, where a certain consistent set of physical differences - including floppy ears - can be observed within all domestic species and are not seen in their wild ancestors.

Having started with dogs, humans also domesticated cattle, horses, sheep, goats, etc.  Each differs from their wild ancestor species in the same set of traits: changed head and facial features, smaller teeth, shorter curly tails, lighter and patchy patterned coats - are all examples of the phenomenon of domestication syndrome in which physical characteristics had emerged along with the tameness. This was interesting yet puzzling, and for a century it remained unexplained.

The domestication syndrome that had been noted by scienctists was unexpectedly demonstrated and was actually duplicated by accident in the 1950s. A Russian geneticist, Dmitry Belyaev who also raised silver fox for their fur, set out on his now somewhat famous 'fox experiment' in Siberia. The experiment was set up to attempt development of a breeding line of tamed silver fox that would be easier to house, handle, and breed than the wild silver fox they were using. In the experimental breeding program, only the offspring that showed the least aggression towards their human handlers were bred for the next generation. Twenty-five years and twenty silver fox generations later, the experiment had created a line of silver foxes who were tame from birth - tame enough that workers and nearby Russian families would take and raise them as house pets - a remarkable result.

The 'fox experiment' produced another dramatic - and unexpected - result: the emergence of certain physical characteristics not seen in the original wild fox, nor in other wild species. The experiment had unwittingly duplicated the domestication syndrome.

Although having been selected only for their temperament, what emerged along with tameness was a set of features right out of Darwin et al.'s Domestication Syndrome: shorter faces, smaller teeth, soft and droopy ears, curly tails, changed colors, and the emergence of different coat patterns that included some foxes having the syndromes's tell-tale white markings on the face. Wild silver foxes never demonstrated any such tameness from birth nor the curly hair, floppy ears, changing coloring, nor variant head shapes that emerged in the later generations of the Russian fox experiment.

The similarity to our dogs' descent from wolves is a clear and fascinating parallel. We witness and participate in the delights of their doggy tameness and enjoy the array of variations of their doggy physical appearance.

Although the unexpected display of the domestication syndrome by the silver fox experiment was a breakthrough finding for genetic and evolution scientists, the question soon became "Why does it happen this way? What is the connection?"

Embryologists believe they have the answer. Scientists are currently testing their theory which suggests that the nature of the embryonic neural crest holds the answer - that the cell type in neural crest development are responsible for producing a number of different cell lines that will eventually dictate both tameness and the physical characteristics that come with tameness.

Cells from the neural crest can become nerves, will effect forebrain development, and will go on  to develop the adrenal glands with their 'fight or flight' hormones. As well, the stress hormone cortisol is produced in the adrenal glands. These structures, their functions, their neurotransmitters produced, and their exact hard-wiring all exist at the roots of tameness, of stereotypical species behaviors, and even spell out the variants in individual behavior.

If it is proven that the neural crest of an embryo is also the source of the cell lines that create the physical characteristics seen in domestication syndrome, then the nature of the embryonic neural crest is the connection, the missing link and becomes the bridge to explain why and how the domestication syndrome occurs - it all derives from the same embryologic structure, the neural crest.

For those of us fascinated by our dogs, this provides a window into the genetics behind the dogginess of dogs.

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