SANTA CRUZ, Calif. – A new study by leading ancient DNA researchers at the University of California, Santa Cruz, used paleogenomics to create a genetic roadmap to help guide the restoration of another iconic species once on the brink of extinction: the North American bison.
Their findings , featured on the cover of the August 6 issue of Science, tell a story that stretches back to a time when the continent's largest land mammal was genetically connected over thousands of miles—though, with regional subspecies emerging within the last few thousand years. Bison went from numbering in the tens of millions for millenia to just a few hundred, mostly due to human activity at the start of the 20th century.
Now rebounding to a total headcount estimated to be in the hundreds of thousands, bison are regarded as a conservation win. But decades of management practices that confined surviving bison to small, isolated herds—and at times bred them with cattle for agricultural experiments—has also obscured their past evolutionary history. Without that, conservationists lack the information needed to restore the bison population through genome-matched breeding.
"Bison are held up as a conservation success story. But until now, managers didn't have a genetic baseline for what 'healthy' bison diversity looked like before 20th century collapse and management," said senior author Beth Shapiro, co-director of the UC Santa Cruz Paleogenomics Lab. "This study builds that baseline using ancient DNA from before the population crash, and is a great example of using ancient DNA to facilitate management decisions in the present."
Over the last decade, the Paleogenomics Lab has revealed new information on ancient species like dire wolves , wooly mammoths , saber-toothed cats , and cave bears .
Understanding bison diversity
For this study, the research team built the largest genomic dataset ever assembled for bison, spanning over 20,000 years. They sequenced the genomes of 160 new bison—115 that lived before the population collapse, and 45 that lived within the last 100 years. Then, they combined that data with 52 published modern genomes. Leading the team were Jonas Oppenheimer, a 2024 Ph.D. graduate from the Paleogenomics Lab , and Shapiro, in partnership with Parks Canada, the University of Alberta, and a large coalition of research institutions and lands stewards across North America.
The two main subspecies of North American bison differ in their overall size, body shape, and coat due to adaptations to their distinct regional habitats. Wood bison, which historically ranged across the forests of northern Canada and Alaska, have a steep hump on their back just behind the head, a less pronounced cape and a small, pointed beard. Plains bison, which originally roamed over open grasslands, prairies, and river valleys stretching from Canada all the way down into northern Mexico, have a hump that sits a bit further back, with thicker capes, and are generally lighter.
A mature male wood bison can exceed a ton, making it the larger subspecies.
The legacy of population collapse
The pressures faced by bison around the turn of the 20th century were truly existential: hunting, new diseases, habitat destruction, and U.S. governmental eradication efforts. Even the early attempts to help restore the population dramatically disrupted the species and the generational gene flow that ensured the bison's ultimate survival through the inheritance of the most beneficial traits.
These early conservation measures included confining bison to isolated herds, which caused population fragmentation of the once genetically connected species. Also, every modern wood bison herd carries some percentage of their plains cousins' genes, which can be traced directly to the Canadian government's translocation of roughly 7,000 plains bison into Wood Buffalo National Park. Located in north-central Canada, the park was home to the last wood bison population of around 1,500 animals at the time.
This study found that the amount of plains ancestry in modern wood bison varies by herd, ranging from 7% to 64%, which now gives managers a genomic guide for basing conservation decisions going forward. Wood bison are listed as "threatened" under Canada's Species at Risk Act, mainly due to the potential loss of genetic diversity from restricted population sizes.
"The research revealed that wood and plains bison are substantially distinct, and should continue to be managed separately despite the introgression event that occurred in the 1920s," said co-author and Parks Canada bison ecologist Greg Wilson.
The myth of cattle ancestry
A genomic blueprint for bison recovery was also blurred by the practice of private herd managers that experimented with cattle cross-breeding during the 20th century. While these efforts were generally unsuccessful, it introduced a persistent belief that most bison today possess cattle ancestry because of these attempts.
By using ancient, pre-cattle bison as a clean genetic baseline—a first for this kind of study—the research team found cattle ancestry in only about a third of modern bison. And when present, Shapiro said, it was a small fraction of the genome—under 2%—and traceable to a limited window of hybridization roughly 20 generations ago.
Restoring cultural and ecological connections
In their paper, the authors also emphasize the vital cultural role bison play in North America, particularly for Indigenous peoples. They assert that these human relationships with the species are just as important to restore as total headcounts, and that paleogenomics may offer another way to contextualize these deep socio-ecological connections.
Lori Cyprien, director of rights and lands for the Athabasca Chipewyan, a First Nation government based in northern Alberta, said "monumental" respect for the species is why her band supports research initiatives such as the Bison Integrated Genomics Project . "The relationship between our people and the buffalo is sacred," Cyprien said. "It is the key to our heritage, traditional lands, and Aboriginal and Treaty Rights."
Ultimately, this study maps out a genomic path for reconnecting isolated bison herds into a functioning metapopulation. It would be the modern-day equivalent of restoring the connectivity bison had for millennia before the 19th-century collapse.
"Ancient DNA is rewriting the story of one of America's most iconic conservation successes," said Shapiro, a professor of ecology and evolutionary biology at UC Santa Cruz, "showing both what the 19th-century collapse actually did to bison genomes and what a smarter, genomically informed path forward could look like."
