Dogs Migrated to America After Humans

Dogs might only have a 10,000-year history in the Americas, suggests a new study that also concludes many early American dogs were wolf-like and highly valued.

The first people who migrated to the Americas did not bring their dogs with them, suggests a new study that concludes dogs likely first came to the Americas only about 10,000 years ago.

If the new research holds true, then the first successful dog migrations to the Americas post-dated the first human migrations by thousands of years. The findings are published in the Journal of Human Evolution.

"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," project leader Kelsey Witt of the University of Illinois said in a press release. "They can be a powerful tool when you're looking at how human populations have moved around over time."

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Witt and her team studied genetic characteristics of 84 sets of ancient dog remains from more than a dozen sites in both North and South America. The study, according to its authors, represents the largest ever analysis of ancient dogs in the Americas.

The data gathered so far on mitochondrial DNA, which is inherited only from mothers, indicates that dogs have a shorter history in the Americas than was previously suspected.

"Dog genetic diversity in the Americas may date back to only about 10,000 years ago," Witt explained.

"This also is about the same time as the oldest dog burial found in the Americas," her colleague Ripan Malhi added. "This may not be a coincidence."

In some samples, the team found significant genetic similarities with American wolves, suggesting that some of the dogs interbred with, or were domesticated anew, from American wolves.

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The study also presents intriguing clues as to what life was like for these earliest American dogs, including how humans valued them.

A site called Janey B. Goode near what is now St. Louis, MO, used to be where the ancient city of Cahokia was located. Cahokia was the largest and first known metropolitan area in North America. It was bustling about 1,000 years ago.

The researchers note that dozens of dogs were ceremonially buried at Janey B. Goode then, suggesting that people there had a special reverence for dogs. While most of the dogs were buried individually, some were placed back-to-back in pairs. The meaning of this remains a mystery for now.

On the downside, at least from a dog's perspective, canine remains were also found with food debris from Cahokia, strongly suggesting that people there consumed dogs for dinner from time to time.

The study also found that there was greater ancient dog diversity in the Americas than previously thought. The researchers, however, found unusually low genetic diversity in some dog populations, suggesting that humans in those regions may have engaged in dog breeding.

There is an important caveat to all of these findings, though.

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"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," Malhi admitted.

Prior research suggests that dogs were in Alaska anywhere from 20,000 to 40,000 years ago. Perhaps some people at those much earlier times had dogs with them, but the dogs were not widespread or formally bred.

If a person did not bury a dog's remains, the chances of finding those remains today - if they even survived weathering - would be extremely challenging.

The story of dogs in the Americas is far from being fully unraveled. Witt and others have more studies in the works.

Photo: A dog-wolf hybrid. Credit: Wikimedia Commons

Facial expressions among social animals appear to have universal qualities, to the point where humans and other animals can discern how certain species feel just by looking at their faces. That's the suggestion in two new studies -- published in the Journal of Veterinary Behavior and PLOS ONE -- that help explain how humans can have such close, understanding relationships with animals such as dogs and horses, the subjects of the investigations. The research confirmed, through animal behavioral analysis, the underlying meaning of dog and horse facial expressions and also demonstrated that people have a natural knack for figuring out what they mean. For example, "this dog is experiencing a positive emotional state, as his owner has just come back," Emanuela Dalla Costa told Discovery News. She led both studies and is a researcher in the Department of Veterinary Science and Public Health at the Università degli Studi di Milano. She explained that the dog’s eyes are wide open, as is his mouth, yet his facial muscles are somewhat tense. Together, these features and others suggest that he is happy, eager and hopeful.

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Here is another happy dog. In this case, Dalla Costa explained, the dog's "lips are retracted, but with no exposure of the teeth." The dog is thrilled that its owner has just returned and eagerly looks to the human for guidance.

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This poor pooch "is tense, due to the departure of his owner," Dalla Costa said. Every part of the dog's face is turned in the direction of his owner's recent exit, maximizing the pup's ability to find him. The dog's eyes and tense mouth convey his worry and loneliness.

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This dog's gaze is riveted on its owner, who is holding food. "This emotional condition is considered positive, and we can assume that this dog is happy," said Dalla Costa, adding that "there is no visible tension in the facial muscles." Even though the eyes, ears and face are pointed in one direction, just as they were for the worried and lonely dog in the previous slide, this hopeful canine feels no anxiety.

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Every aspect of this dog’s face communicates concern and worry. "The mouth is opened and the dog is panting," Dalla Costa said. "The dog’s lips are partly drawn back, with no teeth exposure. The facial muscles show some degree of tension, visible through ridges that emerge on the lateral side of the face and near the eyes." His ears are up, yet not fully open, an indication that he’s attentive but also worried.

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If this dog could talk, the canine would likely be saying, "Oh, please -- feed me." The photo was snapped as the dog looked longingly at its owner, who was holding a favorite food treat. Dalla Costa explained that there is no visible tension in the dog’s face. Its expression cleverly communicates desire and gentleness, while also revealing a sense of hopeful expectation.

Horse expressions, meanwhile, share similar qualities with dogs. This horse, similar to the dogs happily looking at their owners, is attentive and awaiting direction. "The eyes are open and focused on the environment, ears are moving in the direction of sounds, and there is no muscle tension in the mouth," said Dalla Costa.

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This unfortunate horse was photographed while in pain, which, thankfully, turned out to be only temporary. In this moment, however, Dalla Costa noted that the horse's ears are in a sideways position. Its eyes are partially closed, and its "chewing muscles are strained and prominent." Even the horse’s nostrils are stiff over its tightly shut mouth.

While perhaps not as uncomfortable as the previous horse, this horse was also photographed while experiencing temporary, minor discomfort. In this case, the horse’s nostrils are wide open, while its lower lip is drawn back. Even its "ears are held passively backward," Dalla Costa said.

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This horse is completely relaxed. "There is no tension in the mouth and in the chewing muscles," said Dalla Costa. "The nostrils are relaxed." The horse was happy to be chilling out on a pleasant day in an open field.