July 11, 2013
Lineage Of American Dogs Has Pre-Columbian Roots
Brett Smith for redOrbit.com - Your Universe Online
With all the interbreeding that has gone on over the years amongst dogs from around the world, tracing dog lineages can be very difficult.
However, a new study from an international team of scientists has traced canine DNA lineages for uniquely American dogs, like Malamutes and Chihuahuas, back to East Asia -- supporting the theory that humans brought these breeds over the Alaskan Land Bridge that connected the two continents thousands of years ago.
According to study co-author Peter Savolainen, scientists didn't know how much of these ancient breeds were still left in modern dogs.
"The breeds that we are looking at are almost totally pure," Savolainen told National Geographic's Jane Lee.
The evolutionary geneticist at KTH Royal Institute of Technology in Sweden cited the genetic link between a modern Chihuahua and the remains of an ancient dog as one of the most exciting finds in the study, which was published in the Proceedings of the Royal Society B.
"We have a straight line back in time," he said.
In addition to looking at pre-Columbian breeds like the Chihuahua -- Savolainen and his team also examined the genetics of feral dog populations found throughout the Americas. Expecting to find pre-Columbian DNA sequences supplanted by those from Europe, the scientist were surprised to find that certain rural dog populations in Mexico, Bolivia, and the US still have a few ancient genetic markers.
Savolainen said, "What surprised me the most were the Carolina dogs," which inhabit the southeastern US and resemble dingoes.
Previous studies had suggested that the Carolina dog might be indigenous to America, but the team found a specific marker, A184, in its DNA that is unique to East Asian canines.
The researchers said they were able to track these lineages though the millennia by analyzing the dogs' mitochondrial DNA, which is passed from mother to child. They included a large data set of mitochondrial DNA taken from thousands of dogs, along with 19 ancient dog genomes taken from remains found throughout North, South and Central America.
Mitochondrial DNA is much easier for researchers to track than nuclear DNA, which comes from both parents. A genetic process called recombination that occurs in the nucleus makes for a high degree of difficulty when trying to trace a population's origins though nuclear DNA.
However, a major complication with tracing mitochondrial DNA is it only provides half the story, the mothers' half. The research team also acknowledged that they used a limited number of genetic markers, potentially reducing the study's accuracy.
Savolainen said he will begin looking at nuclear DNA in these pre-Columbian dog populations to determine how large the initial population might have been and when the dogs emigrated from East Asia. Some theories have pegged the Asian peoples' expansion into North America around 16,500 years ago.
Unfortunately, the massive data sets necessary for the type of analysis Savolainen wants to perform aren't currently available.
"Researchers are working on building them," he said. "[But] I think it will be a couple of years before you can try this specifically on American dogs."