By sequencing the mitochondrial DNA from ancient North American dogs, researchers from the University of Illinois Urbana-Champaign and elsewhere got a glimpse not only into the history of dogs in the Americas, but also into that of the people who lived with them.
"We were interested in seeing if we could see when dogs arrived in the Americas," first author Kelsey Witt from UIUC tells the Washington Post. "It's assumed they came with humans, but no one has actually looked at it."
Witt and her colleagues report in the Journal of Human Evolution that they sequenced part of the mtDNA from 42 pre-Columbian dogs from Illinois, British Columbia, and Colorado and compared the data they generated to a set of ancient dogs from all over the Americas. From this, they uncovered four novel dog mtDNA haplotypes.
In addition, Witt and her colleagues found low levels of genetic diversity among the dogs at certain sites, suggesting that people were breeding the dogs. They also noted multiple putative founding haplotypes, which could indicate either admixture with North American wolves or a second domestication event.
Around the time the oldest dog was buried, the researchers estimate the effective population size of dogs in the Americas to have been about 1,000 and that it then increased over time.
Dogs also don't seem to have come over to the Americas with the first wave of settlers 15,000 years to 20,000 years ago, but instead came later, possibly with a second wave of migrants some 10,000 years ago, Witt tells the Post.
"I would imagine they were brought because they were useful to the people bringing them," Witt adds. "For whatever reason, they felt they would be helpful as they were migrating."