Humans started living in Fort McMurray, Alta., area at least 11,000 years ago, scientists find

New research may have answered a long-standing mystery by pinning a rough date on the earliest known humans in Canada's oilsands region.

In a recently published paper, professor Robin Woywitka of Edmonton's MacEwan University says a combination of archeology and geology has revealed that people were living around Fort McMurray, Alta., at least 11,000 years ago and perhaps as long ago as 13,000 years ago.

"People were in the Fort McMurray area very early," Woywitka said.

"Fort McMurray has been a nexus for millennia. It's attracted people forever."

Scientists have long known the region has a lengthy human history. An archeological site known the Quarry of the Ancestors has yielded millions of artifacts since it was discovered there in the 1990s.

But putting dates to them has been tough.

Standard methods such as radiocarbon dating are out. The area's acidic soils destroy the organic materials those techniques depend on.

Sometimes, scientists can use sedimentary layers in the earth to date artifacts. But this area has been so stable that there aren't many places where sediment has been deposited.

So Woywitka and his colleagues tried something new.

They took satellite maps that revealed the surface topography with an accuracy to within a few square metres. They used that information to find sites where sedimentation was most likely to have happened and selected five of them — one of them in the Quarry of the Ancestors.

Sediments from those sites were dated using a technique called infrared stimulated luminescence.

That technique exploits the fact sand grains collect tiny radioactive particles in their pores. Those particles deteriorate at a known rate when exposed to light. So, the longer they've been buried, the more particles there will be.

Infrared light causes those particles to release energy. That can then be measured to reveal when the host sand grains were buried, along with the stone tools buried beside them.

In this case, the answer was 12,000 years, give or take a millennium.