Friday, 16 November, 2018

Arrival of European dogs nearly wiped out ancient American dogs

Timeline of the arrival of native North American dogs across the Americas Timeline of the arrival of native North American dogs across the Americas
Gustavo Carr | 09 July, 2018, 15:24

But even the oldest specimens - dating to around 9000 years ago - still lived long after humans first crossed the Bering Strait and established themselves throughout North and South America. Today, that singular genome has all but disappeared, eradicated by the 15th-century arrival of European settlers and their canine companions.

The evolutionary history of dogs has always been a bit murky, as today's dogs are like a "soupy mix" of genes from various breeds, said co-lead study author Angela Perri, a research fellow at Durham University in England.

"By looking at genomic data along with mitochondrial data, we were able to confirm that dogs came to the Americas with humans, and that almost all of that diversity was lost - most likely as a result of European colonization", said Kelsey Witt, who led the mitochondrial DNA genome work as a graduate student in the laboratory of University of IL anthropology professor Ripan Malhi, who also is an author of the study.

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.

When they compared it to the genetic makeup of modern pooches, they confirmed what other scientists have long suggested: The first dogs of North America, similar to Arctic dogs like Siberian huskies or Alaskan malamutes, were brought to the continent when people crossed the land bridge that formed between Russian Federation and Canada. These samples were from 9,000 years ago.

Now, the only remaining lineage of ancient dogs native to North America is a transmissible cancer, according to a new archeological study.

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By far, the introduction of European dogs had the biggest impact.

Findings were published Thursday in the journal Science. But by looking at genes from more than 71 archaeological dog remains in North America and Siberia and comparing them with modern dog genes, the team was able to trace their elusive steps.

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.

"In fact, we now know that the modern American dogs beloved worldwide, such as Labradors and Chihuahuas, are largely descended from Eurasian breeds, introduced to the Americas between the 15th and 20th centuries". Perri tells Wei-Haas that the scientists expected to find evidence of interbreeding between the pre-contact pups and the new arrivals. Finally, Europeans were probably being careful not to interbreed what they thought of as "prized" European dogs with "mongrel native" ones, she said.

Oddly enough, scientists found that the closest surviving trace of pre-contact dogs' DNA is found in a sexually transmitted canine cancer.

Researchers have still not been able to fully pinpoint the exact reasons for their disappearance, and it is something which may remain shrouded in mystery pending further research, but modern American dog populations have nearly nothing in common with their descendants - except one, the canine transmissible venereal tumor (CTVT), a sexually transmitted form of cancer that has spread globally. 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.