November 18, 2025, 5:07 am | Read time: 6 minutes
How much influence did humans really have on the enormous variety of today’s dog breeds? An analysis of dog skulls from the last 50,000 years brings surprising insights to light: As early as 11,000 years ago—long before the previously assumed start of selective breeding—there was an astonishingly wide range of dog forms. Another study also found various differences among the animals and likely the beginning of several lineages of the first breeds. The findings challenge long-held assumptions about the evolution of dogs—with implications for our view of the “best friend of humans.”
Were There Diverse Dog Breeds Even in the Stone Age?
The domestication of dogs is considered one of the earliest human-animal relationships. For a long time, it was assumed that the great physical diversity of today’s dog breeds—from the Chihuahua to the Great Dane—developed only through selective breeding in the Victorian era (1837 to 1901) in England.
Early dogs were seen as relatively uniform in body structure and appearance. Practically like wolves, they were on the path to domestication but still looked like wild animals. However, genetic and archaeological findings paint a more complex picture: While genetic data dates the first domestic dogs to around 11,000 years ago, there is archaeological evidence of domesticated dogs from Siberia that could be up to 33,000 years old.
Have We Misunderstood the Evolution of Dogs?
The study was conducted by Audrey Evin and her international research team at the University of Toulouse. The results on the physical diversity of dogs over tens of thousands of years were published in the scientific journal “Science” (Vol. 390, p. 741, 2025). The precise distinction between early dogs and wolves is often difficult because many remains are fragmentary and look very similar. This is where the study by Evin et al. comes in. The researchers attempted to shed light on the subject with more precise analyses than previously conducted.
They used three-dimensional morphometric methods, analyzing a total of 643 skulls of wild and domesticated canids (dog-like animals) from the last 50,000 years. The method used is based on the precise measurement of fine shape differences using 3D scans or photogrammetry.
The goal was to systematically capture and compare differences in skull shape. The researchers used multivariate statistical methods to identify significant differences. The analysis considered samples that were geographically and temporally diverse.
Early Dogs Were Subject to Natural Selection Pressure
The results show that a distinctly recognizable dog-like skull shape existed as early as around 11,000 years ago, which still aligns with previous genetic analyses. However, the high degree of morphological diversity within the early identified domestic dogs was surprising.
Additionally, it was found that Pleistocene wolves—wolves from the last Ice Age—also exhibited greater physical diversity than today’s wolves. This diversity could have been passed on to their descendants, the first domestic dogs. The researchers, therefore, suspect that environmental factors such as climate or resource availability may have played a larger role in early dog development than human influence.
The wide range of today’s dog forms is thus not solely the result of human breeding but possibly also an inheritance of the diversity of their wild ancestors. This also changes the understanding of the human-animal relationship. Dogs may have changed less through human influence and more through a combination of environmental influences, geographical distribution, and natural adaptation. 1
Ancient Dog DNA Deciphers Early Human Migration Patterns
Another international research team led by Shao-Jie Zhang (Chinese Academy of Sciences), along with over 40 other experts, conducted the most extensive analysis to date of ancient dog genomes from the late Pleistocene and Holocene. The results were also published in the journal “Science.”
The genetic analysis of 73 ancient dogs, including 17 newly sequenced samples, ranged from East Asia to the western Eurasian steppe. For the first time, it shows in detail that the genetic evolution of dogs largely paralleled the spread of human cultures—from hunter-gatherers to sedentary pastoralists.
According to genetic analyses, four main lines of dogs developed as early as around 20,000 years ago—each in East Asia, the Arctic, Europe, and the Middle East. However, where exactly these lines originated and how they spread across the continents is not yet fully clarified. The study now provides new clues.
Dog Migration Mirrors Human History
The genetic data of the dogs show that their lineages shifted multiple times over the course of history. Moreover, they often ran parallel to the migration movements of human groups. For the researchers, this is a clear indication that humans not only kept their dogs but actively took them along on their migrations.
“We see that the genetic signatures of the dogs change as soon as new cultural groups enter a region,” the team stated in the study. These movements can be clearly assigned genetically and run in striking harmony with the spread of human populations.
But there are also exceptions: Dogs from the eastern regions show a distinctly different genetic profile than the humans living there. Although the people there were closely related to Western Eurasians, their dogs came from a more eastern, Arctic line.
Dogs Accompanied Humans Much Earlier Than Previously Thought
Has the Wolf Turned Itself into a Dog?
Dogs as “Biocultural Packages”
This discrepancy suggests that dogs may not only have been companions but also trade goods or cultural bridges between different groups. People may have deliberately exchanged their animals or adopted dogs from other communities.
Particularly interesting is a thesis formulated by Zhang and his team: “The work shows that dogs in East Eurasia played an indispensable role in societies thousands of years ago—as essential ‘biocultural packages’ that traveled with humans.”
The animals thus function as biological archives through their DNA, reflecting trade networks, cultural developments, and environmental changes. Dogs were therefore not acquired only after arriving in a new region but accompanied their owners directly on their migration routes—often over hundreds or thousands of miles. 2
Conclusion
The study results of both investigations make it clear: The millennia-old relationship between humans and dogs was significantly more complex and profound than previously assumed. The evolution of dogs was not a one-sided process of breeding but a combination of nature, culture, and migration. Future studies could help better understand how dogs adapted to different environmental conditions. They could also show how closely their fate (and breeding) was linked to that of humans.