Researchers have discovered how humans got teeth. The researchers are from Sweden. They say that human teeth "first evolved 400 million years ago". They believe our teeth came from an ancient fish. They studied a fossil of the fish. It was difficult to study because the fish is inside rock. They had to use the strongest X-ray machine in the world to "digitally dissect" the fish. The researchers found that the fish's teeth were very similar to human teeth. They also said humans and 60,000 species of vertebrates with jaws living on Earth today come from this fish.
The researchers say the fish was one of the earliest jawed vertebrates with teeth. They were excited at how similar its teeth were to ours. A co-author of the study said: "These 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 trace their origins right back to [that fish]." Another researcher said: "Nobody expected to find teeth so deep on the evolutionary tree."