Scientists have traced the world’s oldest cancer to an 11,000 year old dog, reports the Huffington Post.  Canine transmissible venereal tumor (CTVT) is an extremely rare contagious cancer and is one of only two known diseases in which cancerous cells from one animal infect another.  While most cancer cells remain in their human or animal host, this cancer outlived the dog in which it emerged by spreading its abnormal cells on to other dogs during mating.

According to the Times of India, genome of the CTVT carries about two million mutations, which is many more than are found in most human cancers, the majority of which have between 1,000 and 5,000 mutations.  By looking at a particular type of mutation in the cancer cells from two dogs, an Aboriginal camp dog from Australia and an American cocker spaniel from Brazil, Murchison and colleagues estimated when this original dog lived.  The team used this one type of mutation, which is known to accumulate steadily over time as a sort of molecular clock.  That is how they estimated that the cancer first arose 11,000 years ago.

That dog is considered Patient Zero for the bleeding, ulcerated genital tumor-causing disease.  Also, they were able to extract a few clues to its identity because the cancer cells still contain genetic material from the original dog.  The original dog was likely medium to large in size.  Genetically, it is similar to the current Alaskan malamute or husky.  It carried a mix of genetic variations associated with the domestication of dogs.  Also, one of the dog’s two sex chromosomes disappeared in the cancerous cells.  As a result, researchers could not determine if the dog was male or female, nor could they determine in what part of the world it lived.

Last June, an earlier National Monitor article reported that scientists discovered the oldest tumor in Neanderthal bones that were excavated around the turn of the twentieth century.  The remains containing the tumor were 100,000 years old.  While tumors are generally associated with cancer, this one was associated with another condition called fibrous dysplasia.  Discoveries such as this one and the canine cancer help scientists understand of the history of health and disease.