Researchers say they have discovered how humans got teeth. The researchers are from Uppsala University in Sweden. They say that human teeth "first evolved 400 million years ago". They believe our teeth came from an ancient fish called an acanthothoracid. The researchers studied a fossil of the fish. It was difficult to study because the fish is encased in rock. The researchers had to use the strongest X-ray machine in the world to analyse it. They used the X-ray machine to "digitally dissect" the fish. The researchers discovered that the fish's teeth were amazingly similar to human teeth. The researchers also said humans and 60,000 species of jawed vertebrates living on Earth today come from this fish.
The researchers say the acanthothoracid was one of the earliest jawed vertebrates with teeth ever to live. They were very excited at seeing how similar its teeth were to ours. A co-author of the study, Professor Per Ahlberg, said: "These findings change our whole understanding of the origin of teeth." He commented on the similarity to the fish, saying: "Their jawbones resemble those of bony fish and 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 the first jawed vertebrates." Another researcher said: "Nobody expected to find teeth so deep on the evolutionary tree."