Scientists have solved a mystery that has puzzled us for decades. Ever wondered why birds don’t have teeth? Researchers at the University of California Riverside and Montclair State University have solved this mystery. Birds, along with baleen whales, turtles and anteaters, don’t have teeth. But more than 116 million years ago, a common ancestor of birds had dentin and enamel.
‘Dead genes’ help reveal the secret
“Dead genes” reveal how their common ancestor lost its teeth 116 million years ago. Led by Mark Springer, scientists published findings of their study in the Dec.12 issue of the science Science. They used the degraded remnants of tooth genes in birds to conduct the study. All enamel-less and toothless vertebrates are the descendants of an ancestor with enamel-capped teeth.
The discovery of Archaeopteryx in 1861 showed that modern birds have descended from a toothed ancestor. Archaeopteryx existed about 150 million years ago. It was a transitional species between theropod dinosaurs and birds. It stood on two legs, had wings, and jaws with teeth. Other fossil findings have also showed animals with partial beaks, who still had teeth on the back of their jaws. Springer says it made evolutionary sense.
All 48 bird species share inactive mutations
For this study, scientists looked for shared mutation in six genes that played a crucial role in the formation of enamel and dentin. They examined these genes in the genomes of 48 bird species that represent almost all modern bird orders. Specifically, they looked for the presence of “inactivating mutations” shared by all 48 birds. They discovered that all 48 bird species share inactivating mutations in both enamel-related and dentin-related genes.
It suggests that the common ancestor of birds lost its genetic machinery essential for tooth formation. Springer said it occurred about 116 million years ago. Turtles, pangolin, aardvark and armadillo also had mutations in the dentin and enamel-related genes, making them non-functional. In contrast, all six genes were pretty much functional in the American alligator, which is one of the closest living relatives of birds.
