During most of the Pleistocene Epoch (about 2.5 million to 10 thousand years ago), almost all of Canada was covered in great sheets of ice. The ice came and went a number of times, but it was a dominant force for hundreds of thousands of years. All this time, however, the land of the far northwest—central Yukon and Alaska—remained ice-free and was joined to eastern Siberia by an isthmus of land as broad as Alaska—the Bering Land Bridge. This vast expanse of tundra and grassy steppes is known to geographers and biologists as Beringia.

In June 1993, I jetted westward from Anchorage, Alaska, across the Bering Sea (Fig. 1). As the hills of Chukotka appeared to starboard, a thrill of anticipation ran through me. This trip to Far-eastern Russia was vital to my research …