A new fossil find has set paleontologists abuzz: Ancient nests confirm that bees were alive and well in Patagonia 100 million years ago, marking the oldest fossil evidence for modern bees.

The nests, described recently in the journal PLOS ONE, consist of tunnels studded with grape-shaped alcoves, where the ancient bees’ larvae could mature undisturbed. The only group of living insects that builds nests in this particular way is the family Halictidae, a global and highly diverse bee group also known as the sweat bees. Some modern halictid bees build underground nests that look almost exactly like the newfound fossil burrows.

Since it’s unlikely that some unknown animal happened to construct the same nest architecture, researchers are confident that