The first peoples migrating into the Americas did not bring dogs along, and our canine companions may have only followed on around 10,000 years ago, a new study indicates.
Analysis of genetic evidence from ancient dog remains in both North and South America suggests significant dog migrations followed the first waves of humans only thousands of years later, the study at the University of Illinois found.
"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," said study leader Kelsey Witt. "They can be a powerful tool when you're looking at how human populations have moved around over time."
Analysis of mitochondrial DNA, inherited only from mothers, shows dogs have a more recent history in the Americas than was previously believed, the researchers reported in the Journal of Human Evolution.
"Dog genetic diversity in the Americas may date back to only about 10,000 years ago," Witt said.
Previous studies suggested dogs were in Alaska from 40,000 to 20,000 years ago, and while people of those earlier times may have brought dogs with them, they may not have been widespread, the researchers said.
Some of the dog remains analyzed showed considerable genetic similarities shared with American wolves, the researchers said, pointing to the interbreeding of dogs with wolves.
Or alternatively, early peoples in the Americas could have domesticated dogs anew after their arrival from American wolves, they posited.
Ancient dogs that learned to tolerate human companionship gained benefits, including availability of new food sources and the safety of human settlements, the researchers noted, and they eventually moved across the globe with their masters.
Genetic analysis of ancient dog remains can be a valuable tool to track human migrations since the type of data it yields is rare.
"Living [human] populations who are very connected to their ancestors in some cases may be opposed to the destructive nature of genetic analysis," Witt explained.
Such peoples often permit examination of ancient dog remains even when analysis of human remains is barred, Witt noted.
Four genetic signatures never seen before were found in the new samples studied, suggesting the diversity of dogs throughout the Americas was greater than previously thought, the researchers said.
However, a few ancient dog populations showed unusually low levels of genetic diversity, evidence that some ancient peoples were already engaging in significant dog breeding efforts to fix certain characteristics, they said.
