In Asia’s northern hinterlands not far from the Arctic Circle, Stone Age toolmakers left an evolutionary calling card that’s hard to read.

Artifacts found in this desolate region imply that the toolmakers adapted to frigid temperatures and dark winters, says a team led by archaeologist Ludovic Slimak of the University of Toulouse, France. Around that time, modern human groups in Europe and southwestern Asia underwent pivotal cultural changes. Some groups even reached Arctic spots near the new finds and left behind artifacts associated with that human cultural transition....