The Cave at the Edge of the World

Bluefish Caves are three small solution caves carved by water into a limestone ridge above the Bluefish River, a tributary of the Old Crow River in the northern Yukon Territory of Canada.

The caves sit at the eastern edge of what was, during the last Ice Age, a vast landscape known as Beringia — the land bridge and surrounding territory that connected northeastern Asia to northwestern North America when sea levels were lower.

The Yukon in the present day is a landscape of subarctic boreal forest and tundra, deeply cold in winter, brilliantly lit in summer, traversed by rivers that carry glacial melt from mountains that still hold ice year-round.

But the Yukon of 24,000 years ago was different in ways that matter enormously for understanding what people might have been doing there.

During the Last Glacial Maximum, the great ice sheets that covered much of North America — the Laurentide Ice Sheet to the east and the Cordilleran Ice Sheet along the mountain ranges of the west — did not extend as far north as the Yukon interior.

The area that is now the Yukon Territory, and the broader eastern Beringian landscape, was largely ice-free during this period, creating a refugium — an area of relatively habitable land surrounded by the advancing ice.

The landscape was cold, but it was not glaciated.

It was a steppe-tundra environment, dry and open, with grasses and sedges that supported enormous populations of grazing animals: woolly mammoths, horses, bison, caribou, musk oxen, and other megafauna that are now extinct or much reduced.

This was not a barren wasteland.

It was, by Ice Age standards, one of the most productive landscapes in North America — a cold but functional ecosystem with abundant large-animal prey, running water from rivers like the Bluefish, and the kind of complex terrain — ridges, caves, river valleys — that provides natural shelter and geographic orientation for mobile hunter-gatherer groups.

The caves themselves face southwest, providing some protection from the dominant northerly winds.

They are not large — none of the three cavities is more than a few meters in any dimension — but they are deep enough to provide shelter and, crucially, cold enough to preserve organic material through permafrost that has kept bones from tens of thousands of years ago in remarkable condition.

It was the bone-bearing sediment in these caves that first attracted scientific attention.