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History of Tooth Loss in Modern Birds, 150-Year Mystery Solved

It has long been e mystery as to why modern birds are toothless, but thanks to a new study, this 150-year-old mystery has been solved. From the time of the discovery of the Archaeopteryx fossil in 1861, it has been known that modern birds come from toothed ancestors.

A recent study claims that the loss of teeth in birds occurred 116 million years ago. The study was published in the journal Science by biologists at the UC Riverside and Montclair State University in New Jersey.

modern birds

(Photo: Wikipedia)

Scientists utilized the remains of tooth genes in birds to determine when birds first lost their teeth. The study found that edentulism or absence of teeth used to occur in the common ancestor of all birds.

Mark Springer of UC Riverside, one of the lead authors of the study, said that one of the more important findings of the study is that dead genes – much like the remains of dead organisms – that have preserved in the fossil record have a story to tell. The absence of teeth and a beak are identifying characteristics of modern birds, Springer said.

He also added that the source of origin of enamel-less and toothless vertebrates was their common ancestors which had enamel-capped teeth. For birds, that ancestor is the theropod dinosaur. To process and grind food, modern birds use a beak instead of teeth and a part of their digestive tract. The formation of teeth in vertebrates is a complex process involving multiple genes, the scientists said.

Out of those genes, six of them were highly important and played a crucial role in the creation of enamel and dentin. The scientists analyzed those six genes in 48 bird species genomes, which account for almost all currently-living birds. They found that 48 species of birds share mutations in both enamel-related genes and dentin-related ones.

This suggests that the genetic system needed for the formation of teeth was lost in the ancestor common to all modern birds.

“The presence of several inactivating mutations that are shared by all 48 bird species suggests that the outer enamel covering of teeth was lost around – 116 million years ago,” Springer said.

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