The fossils of bison that roamed near what is now Edmonton 13,000 years ago are helping solve the mystery of the earliest humans in southern Canada, including how and when they got there and where they came from.

The new analysis suggests that for bison, southern Alberta, which had previously been covered in a massive ice sheet, started becoming a nice place to live around 13,400 years ago. 

Around 13,000 years ago, it became a place where bison that once lived north of the ice sheet could meet and mingle with bison that once lived south of the ice sheet, according to a report from U.S. and Canadian researchers in Proceedings of the National Academy of Sciences today. 

'Critical era of human prehistory'

"Any place that one would find bison, one would have to strongly suspect, that human beings could be present too," said University of Alberta archeologist Jack Ives, who co-authored the study.

That offers some hints as to what humans may have been doing in the same landscape at the same time, he added. "This shines some light on a critical era of human prehistory."

Duane Froese with bison skull

Duane Froese, the University of Alberta researcher who coordinated the study, holds a fossil bison skull. The researchers analyzed about 190 bison fossils. (Duane Froese/University of Alberta)

During the last ice age, most of Canada was an inhospitable land covered in a kilometres-thick ice sheets, barren of vegetation and animals.

There's lots of archeological evidence that during that ice age, humans lived north of the ice sheet, in Alaska and the Yukon.

Uninhabitable corridor?

As the climate warmed and the ice sheet melted, an ice-free corridor opened up through central Alberta. For decades, scientists argued about how long it was before that freshly de-iced, muddy landscape would become habitable to humans, allowing them to migrate into the rest of North America.

More recently, scientists have found evidence of humans living south of the ice sheet in places like Florida as far back as 14,550 years ago, suggesting that they got there through another route.

In fact, the earliest human artifacts from southern Alberta date back to around 13,300 years ago. They include thousands of spear points, arrowheads and ancient animal bones, including camels, horses, muskox and bison, found by a schoolteacher at St. Mary's Reservoir in 1996 and later determined to belong to a mysterious culture from a period of time that archeologists know very little about.

But questions about the ice-free corridor — when it opened up and allowed humans and animals to live in southern Alberta and to travel between the north and south — still remained.

The researchers decided to try and answer that question by looking at bison remains.

Both northern and southern groups of people were known to follow bison. "They were definitely on the menu in Alaska 14,000 years ago and certainly were on the menu south of the ice mass," Ives said.

Genetically distinct

Where there were bison, there were also other tasty animals such as camels and horses, along with predators such as lions. The researchers decided to analyze the bison fossils rather than other species because of a genetic quirk — bison in the north and bison in the south were separated from one another by the ice sheet for thousands of years, and were known to be genetically distinct. That would allow the researchers to determine exactly when the two populations reunited, revealing when the corridor was completely open to the movement of bison.

University of Alberta researcher Duane Froese, who coordinated the study, gathered about 190 bison fossils, mostly from the Royal Alberta Museum, and carbon dated them. Peter Heintzman, a postdoctoral researcher at the University of California, Santa Cruz, and the lead author of the report, conducted a DNA analysis to show which fossils came from the northern and southern populations of bison.

Bison fossil skull

The researchers used carbon dating to determine the age of the fossils, and DNA evidence to figure out whether each belonged the northern or southern bison populations. (Yukon Government)

The results show that southern bison started moving north around 13,400 years ago and that the two populations began overlapping in the corridor around 13,000 years ago.

"These two groups were meeting here in Edmonton," Froese said.

He added that while previously, scientists had assumed most populations moved from north to south, the evidence showed movement in both directions.

Ives added, "It's intriguing from the perspective that as much as bison and game animals were separated, so too would have been early human populations, Once that corridor region opened … this would open the door for human populations to reengage."

He's using the new evidence to help plan what to look for on future archeological digs in the region.