Paleontologists at Yale have conducted a shocking experiment to find out exactly how the evolutionary link between dinosaurs and modern-day birds was formed. Instead of scouring the earth for fossils, however, researchers Bhart-Anjan S. Bhullar and Arhat Abzhanov took to the lab to recreate old features on new animals. In doing so, they were able to demonstrate how certain parts of the modern birds’ morphology developed, most notably the beak.

The beak is essential for eating, and is widely specialized across species to perform in different environments. Given the infinite variation in beak shape and function, little was known about the beak’s basic components or how it develops.

In the study, Bhullar and colleagues sought to identify the different parts of the beak, how it develops, and what leads to its development in the first place. After conducting a quantitative analysis of the fossil record to separate the variables they were interested in, they searched for possible changes in gene expression that corresponded to the long and gradual emergence of the beak in bird morphology.

The team compared gene expression in the embryos of chickens, emus, in addition to many other animals without beaks. They found that the birds examined displayed certain genes that were not present in any of the other animals, and that these genes corresponded to facial development in embryos.

The team then used specific molecule inhibitors to block the activity of the proteins produced by the bird-specific genes. They noticed that the embryos developed into normal-looking chickens with one major difference – their beaks were no longer beaks, but rounded snouts. They development of the palatine bones that compose the beak more closely resembled the birds’ ancestral states, reinforcing the link between dinosaurs and modern day birds.

Bhullar hopes that he can replicate his approach to investigate the underlying genetic mechanisms that spurred other major evolutionary transitions.