In 2026, researchers compared ancient and modern bison DNA, finding genetic diversity survived the population collapse

A herd of bison grazing on an American prairie can make it easy to overlook the fact that the species was once brought to the brink of extinction. As a result of commercial hunting and other pressures exerted by humans, the huge herds of bison living in North America were reduced to just a few members. The question then arises whether, along with the population drop, the genetic diversity of American bison was lost as well.

A 2026 study published in Science offers a qualified answer. Researchers, including scientists at the University of California, Santa Cruz, analyzed 115 ancient and 45 modern bison genomes spanning roughly 20,000 years, plus 52 previously published modern genomes. The findings suggest that the collapse disrupted connections between herds more severely than it reduced overall genetic diversity. The UC Santa Cruz account of the research explains that the genomic data could help conservationists make more informed decisions about managing isolated populations.

The research found that historical bison populations were more genetically connected across the continent's interior than they are today. Modern herds have become more isolated through population declines and management practices that confined surviving animals to separate groups. This fragmentation matters because limited gene flow can increase inbreeding risks, even when the species retains substantial genetic diversity overall. In other words, genetic diversity can persist across the species while individual herds become increasingly isolated from one another.

The team also tested claims that cattle ancestry is widespread among modern bison. Early 20th-century ranching experiments crossed the two species, but the extent of that ancestry has remained a concern. Using ancient bison as a baseline, the researchers found evidence of cattle ancestry in 32 of the 97 modern animals they examined. Where detected, it generally accounted for less than 2% of the genome and was traced to crossbreeding about 20 generations ago. None of the ancient animals examined showed cattle ancestry.

Wood bison, the northern subspecies, have a different history of genetic mixing. In the 1920s, Canada relocated roughly 7,000 plains bison to Wood Buffalo National Park. The study found that all modern wood bison herds carry some plains bison ancestry, with proportions ranging from 7% to 64%. Despite this mixing, the two subspecies remained genetically distinct, a finding that supports managing them separately.

To investigate past connections, the researchers studied bison from five archaeological sites in Wyoming, including specimens dating back about 10,500 years, as well as 11 animals from the Bighorn Basin from the past 700 years. The comparisons revealed the ongoing genetic relationships between the bison of Wyoming and other populations from the interior part of the continent. The study also found elevated inbreeding in some modern herds, including the Caprock Canyons State Park herd and two wood bison herds. Connecting targeted populations could help restore gene flow.

Another paper published in 2024 in the Journal of Archaeological Science: Reports studied the bones of bison from Head-Smashed-In Buffalo Jump, a UNESCO World Heritage Site in southwestern Alberta, Canada. Indigenous people hunted bison at the site for thousands of years by driving them off the cliff.

Researchers Rexelle Asis, Skyler Ngo, Mavis Chan, Shawn Bubel, and Theresa M. Burg extracted DNA from 21 long bones and obtained usable results from 17. Most dated to approximately 6,200 to 6,600 years ago. In the study, the team examined mitochondrial DNA, which follows maternal inheritance, and identified five variants among the ancient bison.

Four variants were absent from a comparison group of 240 modern bison, while one was shared with present-day animals. The ancient samples also showed slightly greater variety in this genetic marker. The authors interpreted the results as evidence that the 19th-century population bottleneck was accompanied by the loss of some maternal lineages.

The study has limits. Mitochondrial DNA represents only one part of the genome, and the ancient sample was small. The study therefore cannot establish how much overall genetic diversity disappeared across the species. The shared genetic variant suggests continuity between bison that lived thousands of years ago and those living today. The broader findings may also help conservationists assess how isolated modern bison herds are.