A recent study led by researchers from the University of Exeter and the French CNRS has revealed that the diversification of domestic dogs occurred much earlier than previously thought. This groundbreaking research indicates that distinct differences in size and skull shape among dogs emerged over 11,000 years ago, suggesting a long-standing coevolutionary relationship between humans and their canine companions.
The research, published in the journal Science, examines a diverse collection of dog skulls, showcasing how early canines were already adapting to various roles in human societies. This finding challenges the long-held belief that the significant diversity observed in modern dog breeds is primarily the result of recent selective breeding practices, particularly those that began in the Victorian era.
Global Analysis of Ancient Canine Skulls
Conducted over nearly a decade, the study analyzed 643 canid skulls from both modern and archaeological sources, including recognized breeds, stray dogs, and wolves. This extensive collection spans approximately 50,000 years, from the Pleistocene era to the present day. Researchers created detailed three-dimensional models of each skull and employed geometric morphometrics for precise comparisons of size and shape.
The findings reveal that by the Mesolithic and Neolithic periods, dogs already exhibited a wide variety of skull shapes and body sizes. This early diversity likely reflected the many roles dogs played in human life, such as hunting, herding, guarding, and companionship. According to Dr. Carly Ameen, co-lead author of the study, “Diversity among dogs isn’t just a product of Victorian breeders, but instead a legacy of thousands of years of coevolution with human societies.”
Tracing the Origins of Domestic Canines
Among the significant discoveries, the oldest confirmed domestic dog skull was identified at the Russian Mesolithic site of Veretye, dating back to approximately 11,000 years ago. Similar findings were made in America and Asia, with early domestic dogs appearing around 8,500 years ago and 7,500 years ago, respectively. The skull shapes associated with domestication indicate that variation among dogs increased rapidly after these initial appearances.
The study’s co-lead author, Dr. Allowen Evin, noted that “a reduction in skull size for dogs is first detectable between 9,700-8,700 years ago, while an increase in size variance appears from 7,700 years ago. Greater variability in skull shape begins to emerge from around 8,200 years ago onwards.”
Although modern dogs exhibit extreme physical variations, such as short-faced bulldogs and long-faced borzois, evidence shows that even in the Neolithic period, there was a considerable amount of diversity among dogs. This diversity was already double that of Pleistocene specimens and half the range observed in contemporary dogs.
The research also points to the challenges in identifying the earliest phases of dog domestication. Notably, none of the Late Pleistocene specimens examined displayed skull features consistent with domestication, suggesting that the origins of domestication remain elusive in the archaeological record. Senior author Professor Greger Larson from the University of Oxford stated, “The earliest phases of dog domestication are still hidden from view, and the first dogs continue to elude us. But what we can now show with confidence is that once dogs emerged, they diversified rapidly.”
This study underscores the profound connection between humans and dogs, suggesting that their relationship has influenced each other’s evolution for millennia. As researchers continue to explore the timeline of dog domestication, findings such as these enhance our understanding of the cultural and ecological factors that shaped the evolution of one of humanity’s closest companions.
The research received support from various national and international funding agencies, including the Natural Environment Research Council and the European Research Council, among others. These findings open new avenues for exploring how early human societies and their environments contributed to the diverse forms of dogs that exist today.
