While we all know that cancers are in common to animals and humans, but we're not exactly sure which specie started it all. Scientist though, think that they already know.

Dogs aka man's best friend, might just be the world's oldest cancer patient. Nearly all cancer remains inside an individual until they die but very few - including the sexually transmitted canine cancer - can be transmitted during mating. Scientists believe that this disease has the oldest known line of cancer cells, at 11,000 years old!

Canine transmissible venereal tumor (CTVT) is one of the only two transmittable animal disease ever recorded.

"The cancer cells in all the dogs around the world today are derived from the original dog," said Elizabeth Murchison, a study researcher and cancer geneticist at the Wellcome Trust Sanger Institute and the University of Cambridge, both in the United Kingdom.