It seems the diversity of domestic dogs first began developing thousands of years before humans started intensely shaping modern breeds in the 19th century -- challenging what we thought about canine evolution.
Dog types started to get classified based on appearance or temperament in the 19th century, which eventually led to the breeding programs where one can find today's hundreds of recognized breeds.
In fact, distinctive "dog morphology" -- relating to their body size, skull shape, tail phenotype, fur type and color -- first appeared around 11,000 years ago.
This is according to research led by the University of Montpellier in France and the University of Exeter in England that analyzed the size and shape of hundreds of canid skulls spanning the past 50,000 years, suggesting a more natural origin for the evolution of some breeds.
"Using 3D scans of over 600 ancient and modern skulls, we showed that early Holocene dogs displayed a range of forms comparable to what we see in dogs today. This means that much of the physical diversity we associate with modern breeds actually has very deep roots, emerging soon after domestication," study author Carly Ameen, lecturer in bioarchaeology at Exeter, told Newsweek.
"These results demonstrate that whereas Victorian breeding programs are the origins of many of today's most extreme morphologies, early Holocene domestic dogs exhibited more diverse skull forms than previously considered, corroborating previous studies based on an assessment of canid mandibles," the study authors wrote in the paper.
This suggests the "pressures of human-induced selection alongside changing climatic conditions and food resource availability" would have strongly contributed to diverse dog forms long before modern breeding. Wolf-like characteristics present in some modern breeds also highlights the evolution of the domestic dog from their wild wolf ancestors.
The lack of Pleistocene specimens -- available remains or traces from the Pleistocene Epoch that spanned from around 2.58 million to 11,700 years ago -- and the difficulty of distinguishing early dogs from wolves based only on their skulls has contributed to a gap in research.
To help close this gap, the researchers used the advanced scanning technique to precisely measure subtle differences in shape and size of skulls. Creating digital 3D models through laser scanning or photogrammetry allowed them to compare specific features across ancient and modern dogs and their wild relatives.
This revealed distinct dog-like skull traits first appeared during the early Holocene, after the Pleistocene Epoch ended, with 10,800-year-old remains recovered in Russia.
"Among modern dog breeds, 20 specimens from breeds including the Malakli, German shepherd, St. Bernard, Tibetan mastiff and some hound-like breeds exhibit a 'wolflike' skull shape. Other individuals from these same breeds were categorized as 'dog.' These results highlight the complexity of recognizing domestic individuals in the past," said the authors.
The authors emphasized the results highlight the need for a large-scale investigation of both wild and domestic canid types since the Late Pleistocene "that is not limited by geographical or temporal constraints and does not rely exclusively on modern comparative datasets."
Do you have a tip on a science story that Newsweek should be covering? Do you have a question about distinct dog types? Let us know via [email protected].
Reference
Evin, A., Ameen, C., Brassard, C., Dennis, S., Antipina, E. E., Bonhomme, V., Boudadi-Maligne, M., Britton, K., Cano, F. G., Carden, R. F., Claude, J., Colominas, L., Curth, S., Fedorov, S. E., Frances, J., Kalthoff, D. C., Kitchener, A. C., Knecht, R., Kosintsev, P., ... Larson, G. (2025). The emergence and diversification of dog morphology. Science, 370(6671), 741-744. https://doi.org/10.1126/science.adt0995