This is Alaska today, a wetland of forests, boggy tundra, lakes and rivers — rivers that still churn out fresh clues to the Ice Age past. This is a brick-sized tooth, and it belong to a woollymammoth. Its narrow ridges of enamel tell us more about how mammoths lived.

Studies of modern elephants suggest that the more grass you eat, the more ridges you need. And mammoth’s teeth have even more ridges than those of any elephants. It seems that mammoths fed almost exclusively on grass. They were gargantuan grazers.

Fossil bones help draw a picture of another well-known grazer, a kind of horse. Wild horses live in small herds. And Beringia would have been the scene of vicious battles between rival stallions.

But Beringia’s horses are now gone. Today their closest living relatives roam the open steppes of central Asia. Like mammoths, horses are predominantly grazers.