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- In the largest study of canid remains to date, new genetic techniques allowed two thirds of analysed remains to be classified as dogs or wolves.
- The oldest dog identified (14,200 years old) is already more similar to present-day dogs in Europe than present-day dogs in Asia, suggesting dog domestication began well before this date.
- The dogs that lived alongside European hunter-gatherers were not replaced with the arrival of farming societies, but instead contributed substantially to later and ultimately also modern European dogs.
An international team of researchers led by the Francis Crick Institute, the University of East Anglia and the Max Planck Institute for Evolutionary Anthropology have found that dogs were domesticated more than 14,000 years ago and that dogs living in pre-agricultural Europe contributed substantially to the genetics of dogs living after agriculture and in the present day.
Dogs were domesticated from grey wolves towards the end of the last Ice Age, the first animal to form a domestic relationship with humans, even before the advent of farming.
Researchers are unsure where and how dogs were first domesticated, and, until now, the oldest direct genetic evidence for dogs dates back to just 10,900 years ago. It has typically been difficult to analyse the DNA of older canid (members of the dog family) remains, and studying the appearance of bones does not always allow confident separation of dogs from wolves.
In a study published today in Nature, an international team of researchers deployed advanced genetic techniques in a large project aiming to uncover the identity of Europe's earliest dogs.
They analysed DNA from 216 canid skeletal remains, including 181 samples predating the Neolithic period (before approx. 10,000 years ago), before the invention of farming. These samples came from sites across Europe and its vicinity, including Switzerland, Germany, France, Belgium, the Netherlands, Türkiye, Sweden, Denmark and Scotland. The researchers used a technique called 'hybridisation capture' to boost the amount of usable DNA, designing probes to 'fish out' canid DNA from the large amounts of DNA from microbes like bacteria that tend to contaminate very old remains.
This technique allowed them to identify many early dogs, including a 14,200-year-old dog, one of the oldest dogs confirmed by genetics. It joins a 15,800-year-old dog from Türkiye, analysed as part of a related study into the earliest genetic evidence for domesticated dogs in Türkiye and Europe, also published in Nature today and led by the Natural History Museum, the University of Oxford and LMU Munich.
Identifying dogs from wolves
The scientists first categorised the samples into dogs and wolves by working out how similar each sample is to a present-day dog. Identification as dog or wolf was possible for a remarkable 141 out of 216 remains, with some surprises. A 13,700-year-old canid from Belgium, previously thought to be a dog due to its small size and traces of human modification, was identified as a wolf, demonstrating that genetic data is important to confirm conclusions based on the appearance of remains.
The team also confirmed that a previously proposed dog from the Kesslerloch cave in Switzerland was genetically a dog. At 14,200 years old, this dog is the oldest in this study and one of the oldest ever recorded.
A common origin for ancient dogs in Europe
Previous research from the Crick team suggested that dogs derive ancestry from two distinct wolf sources, one from eastern Eurasia and one from western Eurasia. Using a statistical model, the researchers showed that all the early European dogs in this study can trace their origins to the eastern wolf source, with some showing small amounts of ancestry from the western wolf source.
This new evidence suggests that European wolves didn't contribute detectably to dog evolution, and that early European dogs weren't domesticated independently from dogs in Asia, as both share the same ancestry profile.
The Kesslerloch dog was genetically more similar to European dogs than to Asian dogs, suggesting that dogs were domesticated well before 14,200 years ago, to give time for European and Asian dogs to become genetically different by this time.
Did farming impact dog evolution?
The spread of farming into Europe was accompanied by a large-scale migration of people from Southwest Asia in the Neolithic period. By modelling the ancestry of European dogs after the arrival of Neolithic farmers, the team showed that the dog genetic changes largely mirrored the changes in human genetics, but to a much smaller degree.
This suggests that dogs from local hunter-gatherer groups already living in Europe contributed substantially to the genetics of dog populations living with Neolithic farmers. And genetic analyses of modern European dogs show they are still largely similar to these Neolithic dogs, implying that most common European dog breeds might trace about half of their ancestry to dogs that lived in Europe before farming.
Pontus Skoglund, Senior Group Leader of the Ancient Genomics Laboratory at the Crick and senior author, said: "Dogs were the only domesticated animal to predate farming, so their evolution can help us understand how a big shift in lifestyle shaped our own history.
"It's fascinating that dogs living before the era of agriculture contributed substantially to the genetics of farming and present-day European dogs. Dogs were clearly important to our ancestors, as the first farmers seem to have adopted previous hunter-gatherer dogs into their groups as they moved into Europe."
Anders Bergström, Lecturer at the University of East Anglia, former postdoctoral researcher at the Crick and first author of the study, said: "Without using these advanced genetic tools, we wouldn't be able to confidently distinguish dogs from wolves based on skeletal evidence alone.
"We also wouldn't have been able to put together such a comprehensive view of their evolution. As the Kesslerloch dog, at 14,200 years old, was already more similar to later dogs in Europe than those in Asia, dogs must have been domesticated well before this point, giving time for these genetic differences to emerge. Yet, many questions remain: we're still researching where and how dogs spread across Europe after likely domestication somewhere in Asia. Each piece of evidence is a step forward in this journey."
