Human beings first arrived in North America more than 15,000 years ago according to the most recent findings. However the remains of early Americans are not always available for study. The descendants of those people are frequently not comfortable with the destructive nature of genetic testing. hat cultural sensitivity, however, generally does not extend to dog remains.

For the last 11,000 to 16,000 years dogs and humans have had a unique relationship. Dogs and humans have hunted together, defended one another and worked together. Dogs have served as beasts of burden and helped to protect agricultural land and livestock. At times the dogs themselves were a food source. In other words, where there are dogs there are people and the dogs remains can shed light on their owners culture and history.

A new study, published in the Journal of Human Evolution, examined the genetic characteristics of 84 individual dogs from more than a dozen sites in North and South America.

“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. They can be a powerful tool when you’re looking at how human populations have moved around over time,” said University of Illinois graduate student Kelsey Witt in a statement. Witt, along with anthropology professor Ripan Malhi, led the study.

The study focused on the dogs mitochondrial DNA which, unlike nuclear DNA, is inherited only from the mother. This means that mitochondrial DNA offers researchers “an unbroken line of inheritance back to the past,” said Witt.

Washington State University’s Brian Kemp provided DNA samples from remains found in Colorado and British Columbia. The Illinois State Archaeological Survey (ISAS) provided 35 samples from the Janey B. Good site, located near North America’s first known metropolitan area, an city called Cahokia.

One of the most remarkable finds of the new study was that dogs did not appear in North America until 10,000 years ago. This indicates that the first human arrivals in North America might have been somewhat isolated from other cultures. While there is no certainty as to when humans first domesticated dogs, there is evidence of domestication in Africa, Europe and Asia thousands of years prior to the arrival of the first Americans.

Other findings of the study included four previously unknown genetic signatures in the samples, which suggests greater diversity of dogs than previously thought. Low genetic diversity was found in certain populations which suggests that the humans in those areas engaged in selective dog breeding.

The Cahokia remains were buried individually, or back to back in pairs, suggesting that the people of the ancient city had a special relevance for dogs. Other evidence, such as burial with food debris, suggest that revered or not, dogs were sometimes eaten by the Cahokia’s.

In some populations, the researchers found significant similarities to wolf DNA. This suggests that some of the dogs interbred with wolves, or may have become wild for a period before being domesticated again.

This study provided tests of only a small part of the mitochondrial DNA and more discoveries about the dogs and their owners may be waiting.

“The region of the mitochondrial genome sequenced may mask the true genetic diversity of indigenous dogs in the Americas, resulting in the younger date for dogs when compared with humans,” said Mahli.

Additional studies are in the works and Witt has already sequenced the full mitochondrial genomes of 20 ancient dogs with more to follow.