Long ago, around the end of the last major ice age (about 10,000 years ago), a Malamute-type dog emerged. Existing in small, inbred family groups (or packs) that struggled for survival in a harsh post-ice age environment. These Malamute ancestors fought against the far more powerful wolves that shared the same hunting grounds and often lost. They were too few and not as powerful. They developed a new survival strategy. They frequented the camps of another animal that was more successful than the wolves…humans. Malamute ancestors fed on the leftovers of human hunts, often trailing human camps as they migrated from one area to another. Eventually, Neolithic humans found Malamute puppies orphaned and raised them as pets. Thus began the unique and highly successful partnership…the domestication of the Malamute.
Our story begins with one specific member of one of those packs. We do not know if the dog was male or female, but we do know that it was a Malamute-type dog and not a wolf. It had pointed ears, a medium snout, short straight fur, and most likely, a grey-brown or black coat. It had the ability to digest carbohydrates, a feature not shared with wolves. Make no mistake though, this dog was not our cuddly fur babies. It was more wolf than Malamute and probably had an equally unpleasant disposition.
How do we know all of this? Because researchers at the University of Cambridge analyzed it’s DNA from live cells taken from this dog. Confused? Don’t be. There’s a reasonable, albeit astounding, explanation. This dog’s DNA is alive and well in a form of cancer that exists now, over 10,000 years since that original animal died (and no, no one dug up a skeleton). The amazing fact of the matter is that cells from that original Malamute type dog, exists today in the bodies of countless dogs all around the world.
In what is considered the “oldest continuously surviving cancer we know of in nature”, according to Elizabeth Murchison, a cancer biologist at the University of Cambridge, that original dog has achieved a type of physical immortality through the tragic guise of CTVT (canine transmissible venereal tumor) or Sticker’s Sarcoma.
This infectious cancer had undergone over two million mutations which allowed researchers to compute the approximate age of the cancer line. The DNA allowed them to determine the original host. According to Murchinson, one of the dog’s immune cells became cancerous and grew into a tumor somewhere near its genitals. When this dog mated with another, the cancerous cells were transferred to the other dog. Normally, the other dog’s immune system would recognize the foreign cells and destroy them, however, the early populations of these dogs were highly inbred and shared similar immune markers, so the second dog’s immune system did not recognize it and the cancer grew into a tumor in that dog as well. As each dog, repeated mating with others, the cancer spread. As the cancer spread into other dogs and environments, it mutated, adapting to its new role as a parasite. Its ability to adapt allowed it to spread into other breeds and with new hosts, more mutations occurred.
It wasn’t until the Europeans began to colonize the world that the cancer spread globally via the infected dogs the Europeans brought with them.
Currently, CTVT is a common cancer in dogs with the main reservoir of the disease being free-roaming dogs. In the United Kingdom the incidence of CTVT dropped dramatically when the government enforced new dog control policies and today, there are virtually no reported cases of CTVT in the country.
The other good news about this cancer is that it is very treatable with chemotherapy with over 80% of all infected dogs recovering.
A similar type of transmissible cancer now affects the Tasmanian devil population, threatening to drive the species to extinction if a solution is not found.
For more information on the symptoms of CTVT, CLICK HERE.