A new study suggests that dogs may have first successfully migrated to the Americas only about 10,000 years ago, thousands of years after the first human migrants crossed a land bridge from Siberia to North America.
The study, which looked at the genetic characteristics of 84 individual dogs from more than a dozen sites in North and South America, is the largest analysis so far of ancient dogs in the Americas. The findings appear in the Journal of Human Evolution.
Unlike their wild wolf predecessors, ancient dogs learned to tolerate human company and generally benefitted from the association: they gained access to new food sources, enjoyed the safety of human encampments and, eventually, traveled the world with their two-legged masters. Dogs also were pressed into service as beasts of burden, and sometimes were served as food, particularly on special occasions.
Their 11,000- to 16,000-year association with humans makes dogs a promising subject for the study of ancient human behavior, including migratory behavior, said University of Illinois graduate student Kelsey Witt, who led the new analysis.
“Dogs are one of the earliest organisms to have migrated with humans to every continent, and I think that says a lot about the relationship dogs have had with humans,” Witt said. “They can be a powerful tool when you’re looking at how human populations have moved around over time.”
Human remains are not always available for study “because living populations who are very connected to their ancestors in some cases may be opposed to the destructive nature of genetic analysis,” Witt said. Analysis of ancient dog remains is often permitted when analysis of human remains is not, she said.
Previous studies of ancient dogs in the Americas focused on the dogs’ mitochondrial DNA, which is easier to obtain from ancient remains than nuclear DNA and, unlike nuclear DNA, is inherited only from the mother. This means mitochondrial DNA offers researchers “an unbroken line of inheritance back to the past,” Witt said.
The new study also focused on mitochondrial DNA, but included a much larger sample of dogs than had been analyzed before.