While some American dogs might have been wiped out by epidemics or purposefully killed by Europeans, as indigenous people often were, there are likely other reasons for their demise.
"Although this cancer's DNA has mutated over the years, it is still essentially the DNA of that original founder dog from many thousands of years ago". He noted that we had only sequenced the nuclear DNA of three other ancient dogs until now.
But closer study of the ancient dog genomes shows that they nearly completely disappeared following the arrival of European settlers, leaving little or no trace in more modern American dogs.
The highest level of pre-contact DNA conclusively found in any of the modern dogs was four percent, a negligible result, the New York Times' James Gorman reports. The experts received samples of dogs during the excavations held in the territory of modern IL.
Today these wolf-like dogs are no more.
The researchers were able to show that the native American dogs arrived with the earliest human migrations to North and South America 10,000 years ago. The remains, which date from roughly 10,000 to 1,000 years ago, included those of the Koster dogs, a group of four domesticated canines discovered at a burial site in western IL during the 1970s. A few hundred years later, Europeans came with their domesticated dogs. Instead, these dogs shared an ancestor with the husky. These remains were sourced in the Americas, revealing that a rapid decline in the indigenous dog population took place following the arrival of settlers. The tumor cells spread through mating and carry a copy of that original DNA, allowing researchers to paint a clear picture of the "founding dog", or patient zero.
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Major factors leading to the demise of pre-contact dogs probably include susceptibility to European-borne diseases, systematic persecution by European colonists and a cultural preference for European dogs. But they're still only about 1,000 years old.
Previously the dog family tree was thought to be split into two evolutionary branches- dogs from East Asia, like Chinese village dogs and Tibetan Mastiffs, and dogs from West Eurasia, with modern Arctic dogs falling within both of these groups.
Strangely, the most direct genetic link between ancient American dogs and modern ones is found in a cancerous canine tumor derived from a dog that lived up to 8,000 years ago, the study states.
The research suggests that modern "North American" dogs, such as the Chihuahua, are actually mainly descended from Eurasian breeds introduced to the Americas after the 15th century.
Preserved in every single CTVT tumour is ancient DNA from the long-dead founder. "People are going to be digging up and sequencing bones all over the Americas", Karlsson said.
An extremely good boy undergoing treatment for CTVT.
Perri did not discount that.
While dogs have been man's best friend for more than 10,000 years, a study of their remains found that early dogs likely arrived from Siberia and left a cancerous tumour that is still found in their canine descendants. "This cancer has its own genome", Perri said. If that happens, she added, researchers can "work our way further back in time".
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