A new study suggests that dogs may have first arrived in the Americas only about 10,000 years ago, thousands of years after the first human migrants. The largest analysis so far of ancient dogs in the Americas compared the genetic characteristics of 84 individual dogs from more than a dozen sites in North and South America.
     University of Illinois graduate student Kelsey Witt, who led the new analysis with anthropology professor Ripan Malhi, says that dogs' long association with humans makes them a promising subject for the study of ancient human behaviour, including migratory behaviour.
     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 is inherited only from the mother. The new study also focused on mitochondrial DNA, but included a much larger sample of dogs than had been analysed before.
     As previous studies had done, the Illinois team analysed genetic signals in a special region of the genome. The researchers found four never-before-seen genetic signatures, suggesting greater ancient dog diversity in the Americas than previously thought. They also found unusually low diversity in some dog populations, suggesting that humans in those regions may have engaged in dog breeding. In some samples, the team found significant similarities with American wolves, indicating that some of the dogs interbred with or were domesticated from their wild relatives.
     "Dog genetic diversity in the Americas may date back to only about 10,000 years ago," Witt reveals. "This also is about the same time as the oldest dog burial found in the Americas," says Malhi, adding that the current study likely provides an incomplete picture of ancient dog diversity in the Americas.
     More studies of ancient dogs are in the works. Witt has already sequenced the full mitochondrial genomes of 20 ancient dogs, and more are planned.

Edited from EurekAlert! (7 January 2015)