DNA from a 4,800-year-old dog bone excavated at Newgrange, Co Meath, has led to new findings about the potential origins of man's best friend.
Scientists at Trinity College have sequenced the first ancient dog genome using the bone from the Neolithic tomb, which has led to a new theory about the 'dual origins' of dogs.
While some previously claimed that humans first domesticated wolves in Europe, others claimed this happened in Central Asia or China. However, the new research suggests that both of these claims may be right, meaning that dogs may have been domesticated twice.
Scientists have proven that dogs may have come from two separate - possibly now extinct - wolf populations that lived on opposite sides of the Eurasian continent.
At some point, the eastern dogs mixed with and mostly replaced the earliest European dogs. Most dogs today are a mixture of both eastern and western dogs, which is one reason why previous genetic studies have been difficult to interpret.
This has come about from comparing genetic data with existing archaeological evidence, which has been carried out by a wider team of international scientists.
Senior author of the new body of research Daniel Bradley, the professor of Population Genetics at Trinity College, said it was an important milestone in using ancient DNA to learn about dogs.
"Modern dogs are affected by processes like cross-breeding and mutations which affect their type, colour and illnesses, but this bone was from an original kind of dog," he said.
"It is 4,800 years old, which means it was around at the time of the first farmers at Newgrange."
Although DNA degrades over time, this particular bone was in good condition.
"The Newgrange dog bone had the best preserved ancient DNA we have ever encountered, giving us prehistoric genome of rare high quality," said Mr Bradley. "It is not just a postcard from the past, rather a full package special delivery. We were able to sequence every gene.
"It will now be used in subsequent studies so we hope it has made a huge contribution to the field."
Thousands of ancient dogs and wolves will be analysed to test this new perspective and establish the timing and location of the history of our oldest pet.
'Genomic and archaeological evidence suggest a dual origin of domestic dogs', the paper which contains the findings, is published in international journal 'Science'.