About 6,000 years ago, an unfortunate dog suffered from a relatively rare form of cancer. Since then, unlike any other cancer, its cancer cells were swiftly transmitted from one dog to another. Today, this age-old ailment has a name—Canine Transmissible Venereal Tumour or CTVT.  In a  recent study, they traced the history of CTVT to Asia, and in the process, helped understand the evolution of cancer in the long term.