Researchers from Sweden have found how humans got teeth. They say human teeth "first evolved 400 million years ago" from an ancient fish. They studied a fossil of the fish. It was difficult to study because the fish is inside rock. They used the strongest X-ray machine in the world to look at the fish. They found that the fish's teeth were very similar to human teeth. Humans and 60,000 species of vertebrates on Earth today come from this fish.
The fish was one of the earliest jawed vertebrates with teeth. A researcher said: "[Our] findings change our whole understanding of the origin of teeth." He said: "Their jawbones...seem to be directly ancestral to our own. When you grin at the bathroom mirror in the morning, the teeth that grin back at you can [follow] their origins right back to [that fish]." Another researcher said: "Nobody expected to find teeth so deep on the evolutionary tree."