Some 10,000 years ago, in what is now Koster, Illinois, a dog died. Its adopted group of hunter gatherers carefully laid the pup to rest in its own grave among their buried human dead, curled on its side as if it were asleep.

Today, this may not seem surprising — after all, modern dogs are often more “fur baby” than pet. But this ancient Illinois dog, and a duo of other canines buried right nearby, are remarkable: They're the oldest known individually buried canines found anywhere in the world, according to new research on the pre-print server Biorxiv. What's more, they provide the earliest physical evidence for dogs in the Americas.

The remains of these creatures has also proved key to