How Early Did Humans Domesticate Dogs? Ancient DNA Reveals New Clues

The story of how dogs became our companions just got a significant rewrite. New genetic studies, published March 25 in Nature, push back the confirmed date of dog domestication by over 3,000 years, suggesting a close relationship between humans and dogs existed at least 14,200 years ago. This discovery challenges previous assumptions about the origins of our canine friends and offers a deeper understanding of the complex interplay between early humans and animals. ScienceNews reports on the findings.

A Timeline Rewritten: From Wolves to Companions

For decades, scientists have debated when and where dogs were first domesticated from gray wolves (Canis lupus). Previous research, including a 2015 study analyzing fossilized wolf bones from Siberia, estimated the split between dogs and wolves occurred between 27,000 and 40,000 years ago. However, concrete genetic evidence confirming this timeline, particularly for early European dogs, remained elusive. The oldest previously confirmed dog remains with preserved DNA, found in northwest Russia, dated back only around 10,900 years.

The new research, detailed in Nature, analyzed ancient DNA extracted from over 200 sets of dog and wolf remains discovered at prehistoric sites across Europe, Southwest Asia, and the Iranian plateau. The pivotal discovery came from a dog found at the Kesserloch archaeological site in Switzerland, radiocarbon-dated to 14,200 years ago – during the Paleolithic period. This makes it the oldest confirmed dog with analyzable DNA to date.

What the Ancient DNA Reveals

The genetic analysis of the Kesserloch dog revealed a surprising connection to modern dogs worldwide. Rather than being a separate domestication event unique to Europe, the Kesserloch dog shared ancestry with dogs from other regions, suggesting a common origin. This finding refutes the hypothesis that European Upper Paleolithic dogs evolved entirely independently from European wolves. The data indicates these early European dogs reached the continent by 14,000 years ago, sharing a common ancestry with dogs elsewhere.

Further analysis of genomes from sites in present-day Turkey, England, and Serbia showed that genetically stable dog populations were established across this broad region by approximately 14,300 years ago. The consistency of genetic signatures across these sites suggests these were not isolated incidents but rather established, thriving dog populations.

Beyond Genetics: Behavioral Clues

While the genetic evidence provides a firm timeline, archaeological findings offer hints about the nature of the early human-dog relationship. Researchers don’t definitively recognize if these ancient dogs were fully domesticated “pets” in the modern sense, or if they simply frequented human campsites. However, evidence suggests at least one of the dogs was well-cared for by humans, indicating a level of tolerance and potentially even affection. This supports the idea that early dogs were well-tempered and integrated into human groups.

Tracing Ancestry and Migration

The studies as well uncovered traces of Southwest Asian ancestry within some ancient European dog genomes. This suggests that the migration of farming people from Southwest Asia into Europe around 9,000 years ago also involved the movement of dogs, contributing to the genetic diversity of European canine populations. Interestingly, the researchers found that the influx of Southwest Asian ancestry into dogs was smaller than that observed in humans, suggesting that Mesolithic dogs (those present before the arrival of farmers) played a substantial role in shaping the genetic makeup of subsequent European dog populations, and likely even modern ones.

What Does This Mean for Our Understanding of Domestication?

These findings reinforce the idea that dogs originated from wolves between 27,000 and 40,000 years ago, but clarify the path of their spread and evolution. Adam Boyko of Cornell University, who studies dog genetics but was not involved in the new studies, notes that the research supports the theory of a single domestication origin, likely somewhere in Asia, followed by interbreeding between early dogs and wolves. He cautions, however, that it’s still possible some early fossils classified as wolves were, in fact, already domesticated dogs.

The Ongoing Search for Origins

As evolutionary biologist Beth Shapiro of the University of California, Santa Cruz, who was not involved in the new work, explains, the more ancient dog DNA scientists can analyze, the closer they will obtain to pinpointing exactly when and where the remarkable partnership between humans and dogs began. Future research will likely focus on expanding the geographic scope of DNA analysis and refining the techniques used to extract and analyze ancient genetic material.

The process of understanding dog domestication is ongoing. Researchers continue to analyze ancient genomes, refine dating techniques, and explore archaeological evidence to build a more complete picture of this pivotal moment in human and animal history. Further studies will also investigate the specific genetic changes that occurred during domestication, shedding light on the evolutionary processes that transformed wolves into the loyal companions we know today.