Innocent backyard chickens appear to harbor genes to grow a Velociraptor-like snout. After blocking two proteins that are activated when chicken embryos grow their beaks, researchers discovered how bird beaks may have evolved. To their surprise, and the hen’s dismay, dinosaur-like snouts and palates developed on embryos close to hatching.
“This [discovery] was unexpected and demonstrates the way in which a single, simple developmental mechanism can have wide-ranging and unexpected effects,” said Bhart-Anjan Bhullar, lead author of the study, from Yale University and co-led by Arhat Abzhanov, Bhullar’s doctoral supervisor at Harvard University.
Scientists believe that birds evolved from dinosaurs, but with very different jaws. A modern bird has fused premaxillae–bones that are fused to form a beak. A bird-like dinosaur such as Velociraptor, had two bones at the tip of their upper jaws. When researchers blocked the two proteins in chickens that would normally form the beak, they caused their jaws to “revert” to this ancestral phenotype (physical display of a genetic characteristic).
(Artist’s interpretation of dinosaur Anchiornis (back) and modern bird Tinamou (front) to show difference in bones at tips of their jaws. (John Conway/Yale University)
To uncover what is needed for beak development, Bhullar and his colleagues looked at the gene expression domains (areas in the DNA that determine what will develop) in the embryonic face: the earlier frontonasal ectodermal zone (FEZ) and the later midfacial Wnt-responsive region. They compared the activation of genes (causing the genes to be used by the organism) during embryonic development in birds to that of lizards, crocodiles, and turtles as their jaws formed. They found two proteins that were only activated in birds, which were the ones they blocked during their experiment. These were the genes responsible for the mutations that caused a “jaw” instead of a beak on the chickens. The results uncover a possible “missing link” species between dinosaurs and birds.
In past experiments, chicken embryos have been shown to be related to dinosaurs. In 2006, German scientists identified a genetic mutation that caused chicken embryos to grow teeth. Farmers may begin to advocate for the stop of embryonic experimentation to prevent Velociraptors in the hen house and their chickens needing an orthodontist.
An avian beak is considered a key evolutionary innovation, as it allows birds to adapt in a variety of ecosystems. The results of the Velociraptor-snout experiment are published in The International Journal of Organic Evolution.
