CAMBRIDGE, England — The longest-living continuous strain of cancer has been surviving in dogs for 11,000 years, according to a study released Thursday.

Researchers traced the cancer back to a single dog that lived 11,000 years ago using genetics. The cancer is transmissible and causes genital tumors in dogs even today, according to a study by the Wellcome Trust Sanger Institute and the University of Cambridge.

"The genome of this remarkable long-lived cancer has demonstrated that, given the right conditions, cancers can continue to survive for more than 10,000 years despite the accumulation of millions of mutations," said lead author Elizabeth Murchison in a statement.

Since the cancer was transmitted by the original dog through mating, it has spawned about 2 million mutations, according to the study. By looking at the genetic code of the different variations of the cancer, researchers said they believe the first dog to develop the cancer would have resembled a Husky or Alaskan Malamute and had short, straight brown or black fur.

While they said they don't know if the dog was male or female, they could tell it was the result of inbreeding.

"We do not know why this particular individual gave rise to a transmissible cancer," Murchison said. "But it is fascinating to look back in time and reconstruct the identity of this ancient dog whose genome is still alive today in the cells of the cancer that it spawned."

Scientists said the cancer stayed in one group of dogs for most of existence before spreading world-wide 500 years ago. They think it moved to other dog populations when sailors started taking dogs with them on explorations.

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Transmissible cancers are very rare, researchers said. Other than this cancer in dogs, they said the only other known transmissible cancer is found in Tasmanian devils who bite each other.

By tracing the cancer in dogs they hope to better understand how cancer can mutate and spread to other parts of the body.

"The genome of the transmissible dog cancer will help us to understand the processes that allow cancers to become transmissible," said senior author Mike Stratton in a statement. "Although transmissible cancers are very rare, we should be prepared in case such a disease emerged in humans or other animals. Furthermore, studying the evolution of this ancient cancer can help us to understand factors driving cancer evolution more generally."

The study was published in the journal "Science."

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