How Birds Lost Teeth - Have you ever wondered why birds do not have teeth? There are over 10,000 species of birds across the planet. And despite their differences, they all share a common trait- edentulism (the absence of teeth).

For decades evolutionary scientists have wondered how birds lost their teeth. Researchers say birds lost teeth more than 100 million years ago. According to a new study, which was published in the Science Magazine on Dec.12, birds lost teeth through a common ancestor who had enamel-capped-teeth.

"Ever since the discovery of the fossil bird Archaeopteryx in 1861, it has been clear that living birds are descended from toothed ancestors," Mark Springer, the lead researcher in the study said.

"However, the history of tooth loss in the ancestry of modern birds has remained elusive for more than 150 years," he added.

A team of genetic researchers from the University of California, Riverside and Montclair State University as well as New Jersey collaborated to conduct the study. They sought to discover how avian edentulism became the norm in all living birds.

In order to scientifically answer the question on how birds lost teeth, scientists used a combination of different genes essential for the optimal formation of dentin and enamel - agents that produce teeth, which are inactive in the avian genome. Although they remain inactive, these genes are still present in birds.

This genome database contains all the genetic history of almost all living birds- 48 species in total.

"One of the larger lessons of our finding is that 'dead genes,' like the remnants of dead organisms that are preserved in the fossil record, have a story to tell," Springer explained in a statement."DNA from the crypt is a powerful tool for unlocking secrets of evolutionary history."

The team of researchers, who come from Australia, China, Denmark and the United States, carefully examined the genome of the 48-bird species. 

The results revealed that nearly all modern birds shared the same mutation which deactivated their teeth producing genes. Researchers postulate that all birds lost their teeth after inheriting genes from a common ancestor, who lived about 116 million years ago.

"The presence of several inactivating mutations that are shared by all 48 bird species suggest that the outer enamel covering of the teeth was lost around 166 million years ago," Springer said.

The study also discovered that six of these genes are still present and very active in crocodylia (the closest relative to all modern birds). And different inactive types of the genes resulting in different mutations can be found in other animals without teeth, including anteaters and turtles.