<p>One fall day in Interior Alaska, a lion stalked a ground squirrel that stood exposed on a hillside like a foot-long sandwich. The squirrel saw bending blades of grass, squeaked an alarm call, and then dived into its hole. It curled up in a grassy nest. A few months later, for reasons unknown, its heart stopped during hibernation.</p> <p>Twenty thousand years later, Ben Gaglioti is teasing apart the mummified ground squirrel’s cache in an attempt to better reconstruct what Alaska was like during the days of the mammoth, bison, wild horse and camel.</p>