Fed by damp wood and burning fitfully, the fire lights the recesses of the rock shelter where a group of people wrapped in furs huddles for warmth. Outside, a freezing rain falls. They are on the southern edge of an immense glacier, in what today is Wisconsin. The glacial sheet also grips much of Minnesota and Michigan, but it is melting, and the rivers roar with chunks of ice and debris.

The glacier’s demise shapes everything they will encounter in the time to come. The Midwest is a work in progress, scoured by small continents of ice, flooded by runoff that fills gorges and depressions. The region is at the mercy of a fluctuating climate, ruled by an ice cap at the top of the globe. The Great Lakes are mercurial inland seas, swelling, shrinking, and sculpting the land. 

From the rock shelter’s entrance, two men read the landscape, forming topography and climate into mental roadmaps and almanacs that help them decide whether to continue. They will need to remember this shelter in case the journey goes badly. The trek is slower with the elders along, but their knowledge is invaluable. They speak of a time when a body of water covered this very place.

Outside the sleet fades, leaving a glistening coat on budding branches. The men examine their spear points, touching up dulled edges by striking them with hammers made of animal horn and re-securing the sinew binding around the wooden hafts. They keep an eye to the ground for chert, stone for their weapons and tools. With a murmured agreement that the time has come, the small group douses the fire, gathers the children, and moves on.