Long before the first terrier, retriever, shepherd or toy breed crossed the pond, America was populated by dogs who could trace their roots back nearly 15,000 years.
This ancient and now-extinct breed was the subject of an in-depth study by an international team of 50 scientists, including one University of Iowa researcher, Andrew Kitchen. “The evolutionary history of dogs in the Americas” was published in the journal Science on July 5, presenting evidence that humans weren’t alone when they crossed the Bering Land Bridge to North America around 10,000 years ago.
“Native Americans brought dogs with them into the Americas as part of their adaptive toolkit,” said Kitchen in an email to Little Village. Kitchen is a UI associate professor of anthropology who contributed to the study by analyzing the mitochondrial genomes of the ancient dogs.
Exactly when dogs were first domesticated is an ongoing debate — scientists estimate anywhere from 10,000 to 40,000 years ago — but they are widely regarded as the first domesticated mammal. Kitchen said the “indispensable” roles dogs have played in human life — as hunters, herders, guardians, pack animals and much more — make dogs a popular subject of anthropological study.
“It turns out that dogs are as close as a universal cultural trait as there is,” he said. “Almost all human populations have, or had, dogs. Additionally, dogs may be good models for the development of increased sociality and decreased aggression in humans (which is unique amongst the great apes). They are also cute and cuddly.”
America’s first cuddly companions were tracked using a rather grim feature of their DNA: sexually transmitted tumors. Canine transmissible venereal tumor (CTVT) is a fascinating phenomenon in itself: it’s a cancer that can pass from dog to dog via sex, originating thousands of years ago, likely in East Asia. Scientists are able to sequence DNA from the genes of CTVT cells in ancient dog remains as well as modern dogs to track canine family trees back across continents and millennia.
“The common ancestor of all of the pre-Columbian dog maternal lineages lived [approximately] 14,600 years ago,” Kitchen said. “This matches up very well with our current thoughts about when the peopling of the Americas occurred.”
America’s ancient dog breed is referred to as pre-Columbian or pre-contact because it began to disappear not long after Christopher Columbus and the thousands of Europeans who followed him invaded the Americas around 500 years ago. Kitchen called the loss of the pre-contact dog “tragic.”
“European colonization effectively wiped out the gene pool of pre-Columbian dogs, replacing it with a gene pool consisting of European dog alleles,” he said. “[It’s] indicative of the negative consequences of European colonization on the indigenous American populations.”
The fate of pre-contact dogs could be compared to that of Neanderthals, whose extinction is thought to have been caused, in part, by contact with humans — the result of violence, displacement and/or interbreeding. Some modern humans still carry more than 2 percent Neanderthal DNA; the pre-Columbian dog researchers found up to 4 percent pre-contact dog DNA in the modern dogs they tested, but that percent falls within the error range of the tests in the research.
Kitchen said his ancient dog study was part of widespread collaboration between archaeologists, biological anthropologists and geneticists from Cambridge to St. Petersburg, Paris to Vancouver, and two dozen cities in between. He was asked to join the study by Ripan Malhi and Kelsey Witt of the University of Illinois. Internet communication was invaluable to the process.
“Researchers from other groups working on aspects of pre-Columbian dog genetics became aware of each other through the dissemination of results at conferences and through peer-to-peer networks,” Kitchen explained. “It was then decided to merge the multiple lines of research into one larger project. This larger project would tell the story of dogs in the Americas more holistically than any one line of analysis alone.”
From pre-Columbian dogs to European purebreds, Kitchen said he’s come to look at man’s best friend in a new light as a result of his studies.
“I have grown to appreciate how important they were as companions and tools to human populations over the past 10,000-plus years,” he said. “They played multiple roles in human cultures, and they spread throughout the world, most likely because they were useful. It is important to understand that our current conception of dogs is quite modern, and that dogs were originally domesticated as work animals first and companions second. Knowing that, I still adore my two dogs as companions, despite their utter lack of utility when it comes to domestic labor.”
Kitchen is currently studying the history of Native American dogs on the American plains with fellow UI anthropology professor Matthew Hill, as well as other, non-canine projects looking at the spread of tuberculosis around the globe, the origins of human infectious disease and the diversification of languages in Africa and the Middle East.
“It’s a fun time to be a geneticist interested in human history,” he said.