New research in Science drew on three-dimensional analyses of 643 ancient canid skulls to show that the range of shapes seen in modern dogs began deep in prehistory; the team created digital models of recognized breeds, village dogs, wolves and prehistoric specimens spanning 50,000 years, according to a report by Scientific American.

Archaeological and genetic evidence indicated that people lived closely with wolves for at least 30,000 years and that major dog lineages were present by 11,000 years ago, BBC News reported.

The project, led by the French National Centre for Scientific Research, used geometric morphometrics to track skull changes. Digital scans showed the first clearly dog-like head around 10,800 years ago at Veretye in Russia, just after the Pleistocene–Holocene transition. “We were surprised by how variable the early dogs already were… around 11,000 years ago, dogs already showed approximately half the cranial diversity observed today,” said Allowen Evin of CNRS, according to Phys.org.

Earlier Late Ice Age skulls looked almost identical to wolves, and none of the 17 re-examined Pleistocene specimens crossed the threshold to be classed as dogs. “Once dogs appeared, they diversified rapidly,” said Greger Larson of the University of Oxford, according to GEO France.

By the Mesolithic, skull variation had reached half the span seen in modern breeds. “This means much of the physical diversity we associate with modern breeds actually has very deep roots, emerging soon after domestication,” said Carly Ameen of the University of Exeter, according to ABC News Australia. She added, “It’s likely to be a combination of interaction with humans, adapting to different environments, adapting to different types of food—all contributing to the kind of explosion of variation that we see,” according to BBC News.

Genomic data published in the same issue supported these findings. Sequencing of 17 ancient dogs from Siberia, the Central Eurasian steppe and northwest China showed that canids moved with people across Europe, Asia and the Arctic for at least 10,000 years. “This tight link between human and dog genetics shows that dogs were an integral part of society, whether you were a hunter-gatherer in the Arctic Circle 10,000 years ago or a metalworker in an early Chinese city,” said Laurent Frantz of Ludwig Maximilian University of Munich.

The results challenge the idea that Victorian kennel clubs created most canine diversity. “It starts to challenge the ideas about whether or not it was the Victorians—and their kennel clubs—that drove this,” said Ameen, according to BBC News. The authors wrote that early Holocene animals already displayed more diverse skulls than previously assumed and that human selection, shifting climates and changing food resources drove early diversity, Newsweek reported.

Some ancient dogs retained wolf-like heads, a pattern echoed in breeds such as German shepherds and Tibetan mastiffs. The presence of these forms “highlights the complexity of disentangling the biological and cultural status of the earliest domestic individuals,” according to the Independent.

Pinpointing the exact moment wolves became dogs remains difficult. “The very first phases of dog domestication remain invisible, and the first dogs continue to escape us,” said Larson, according to GEO France. Researchers said more material from the crucial 25,000–11,000-year window, especially from Central and Southwest Asia, was vital.

“Early humans influenced which animals thrived around them—whether intentionally or not—but environmental and ecological pressures also played an important role,” said Evin, according to Phys.org.

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