KU Natural History Museum's senior curator helps track rise and fall of bison

LAWRENCE -- Conventional thinking concludes that the near extinction of the bison in North America was the result of indiscriminate hunting by humans, which left only a few hundred bison alive by the end of the 19th century.

Recent research published last week in the journal Science, however, shows that global climate changes dealt a considerable blow to the bison long before humans became a part of the bison's decline. Larry D. Martin, senior curator of the Natural History Museum and Biodiversity Center at the University of Kansas, was part of a team of 27 scientists who conducted DNA analysis of 442 bison fossils found in Siberia, China and Canada, as well as Alaska and Wyoming, to make the surprising conclusion.

“ Bison have a very low genetic diversity today,” said Martin, KU professor of ecology and evolutionary biology. “We were never surprised by this because we knew that huge populations of bison had been killed by human hunting. The shocking thing is that before that happened, Mother Nature nearly took the bison out. That's a new discovery.”

Today, there are only two subspecies of bison left in North America, the plains bison and the wood bison, Martin said. During the middle of the Pleistocene epoch (about 500,000 to 130,000 years ago), however, a large number of genetically diverse bison migrated from Asia, across Beringia (now the water and land areas between Alaska and Siberia) and spread east across Canada and southward across the United States, including Kansas.

Then about 20,000 years ago, the Last Glacial Maximum began.

“ It was a worldwide event,” Martin said. “It's the coldest the earth has been in the last 350 million years.”

Lasting about 10,000 years, the Last Glacial Maximum caused an ice barrier to form between Canada and the United States, separating the bison into northern and southern populations. The bison north of the ice barrier failed to survive, Martin said. The southern bison were almost wiped out but survived, although with less genetic diversity than before.

“The modern bison that we have today are all descendents of the populations that were south of the ice barrier,” Martin said. “Prior to this research, scientists had argued that the modern bison were from the northern populations of bison that moved south. We now know that the opposite occurred.”

The study was made possible by the high quality of DNA preservation in the fossils found in the frozen ground in Siberia, China and Alaska, Martin said. Beth Shapiro of Oxford University in England was the lead researcher on the study.

For his part in the study, Martin studied bison fossils from Natural Trap Cave near Lovell, a community in north-central Wyoming. The cave features an 85-foot drop straight down and contains thousands of well-preserved animal fossils.

Martin has been extracting fossils from the site since the '70s, and the Natural History Museum is home to all of the fossils that have been discovered in the cave.

“ Natural Trap Cave is one of the most important spots for fossil DNA in the world,” he said. “When we were first digging there years ago, no one thought we could get DNA out of those bones. The technique was only perfected in the 1990s.

“ We've collected more than 40,000 bones from Natural Trap Cave and only collected about 5 percent of what's there. That cave will yield new discoveries for generations.”