The North American plains bison stands as a symbol of both rampant devastation wrought by colonizing powers and of the potential to bring a species back from the brink of extinction.

The legacy of that destruction, and the promise and perils of the recovery, are indelibly etched in the DNA of the survivors and their ancestors, according to research just published in Science.

“Ancient DNA is rewriting the story of one of America’s most iconic conservation successes,” said Beth Shapiro, a University of California Santa Cruz researcher and the paper’s senior author. The new results show “both what the 19th-century collapse actually did to bison genomes and what a smarter, genomically informed path forward could look like.”

For millennia, an ocean of bison numbering in the millions swept across the center of North America, shaping ecosystems and the Indigenous peoples who lived there. But by the early 20^th century, there were just a few hundred left, their numbers depleted by overhunting, habitat loss and systematic slaughter sanctioned by the U.S government to help subjugate bison-dependent tribes.

Since then, conservation work by some of these same tribes, and others, has led to a modest recovery. Today, more than 20,000 bison live in the wild, largely in protected land such as Yellowstone National Park. More than 400,000 are raised for commercial uses such as meat.

But the recovery has been dogged by questions. Since current bison are descended from such a small population, have they lost genetic diversity or become inbred? Did a quixotic attempt to breed bison with domesticated cattle irreversibly tamper with their genetics? Similarly, did a decision to move thousands of plains bison into the territory of wood bison break down the genetic wall between the closely-related species?

To answer these questions, Shapiro and colleagues turned to the latest scientific tools for deciphering a species’ history in its DNA. They collected samples from 115 ancient bison, dating back as much as 20,000 years and as recently as 100 years ago, when the last survivors of the slaughter remained. They also gathered tissue from 45 modern-day bison.

When they sequenced the genomes, the results offered both good news and cautionary lessons about the current state of bison conservation.

Among the ancient samples, the genetics of plains bison were remarkably similar regardless of their location. That suggests a genetic flow across the landscape relatively uninhibited by geography. By contrast, today’s wild plains bison are confined to small pockets of land. There are at least four groups with distinct, shared genetic fingerprint that differs from the other groups.

The findings point to the need for managing the remaining bison more as a single herd, the authors write. Given the geographic barriers, that could mean using modern reproductive techniques to help blend the DNA of these different herds, much as modern cattle are carefully bred using tools such as artificial insemination.

While this points to the potential risks of continuing with traditional management methods, the findings also show reasons to be hopeful. Although the modern herds are distinct from each other, collectively they contain levels of genetic diversity similar to their ancestors.

Fears of contamination from cattle also appear to be overblown. The analysis turned up traces of livestock DNA in roughly a third of the modern-day bison genomes. That means the majority of bison hadn’t been tainted. And in those that did contain evidence of cattle, it represented less than 2% of their genomes.

The news is slightly more complicated for wood bison, the larger relative of the plains bison that lives in Canada’s boreal forest. In the 1920s, the Canadian government moved around 7,000 plains bison into Wood Buffalo National Park, which at the time was home to the last surviving 1,500 wood bison.

The legacy of that transplant remains today. The study showed that wood bison are genetically distinct – having diverged from plain bison approximately 3,000 years ago. But it also revealed that today’s wood bison carry significant plains bison DNA. The individual wood bison genomes were between 7% and 64% from plains bison.

Despite this, the results show “that wood and plains bison are substantially distinct and should continue to be managed separately,” said Parks Canada bison ecologist Greg Wilson, a coauthor of the study.

Now, thanks to DNA, bison managers have a clearer roadmap for moving forward, and the tools to know if they are veering further off course.

“Until now, managers didn’t have a genetic baseline for what ‘healthy’ bison diversity looked like before the 20th-century collapse and management,” said Shapiro. The new study “is a great example of using ancient DNA to facilitate management decisions in the present.”

Oppenheimer, et. al. “Paleogenomic insight into the collapse, recovery, and management of American bison.” Science. Aug. 6, 2026.

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