Chicken embryos with dinosaur snouts have been created in a laboratory, shedding light on the evolution of beaks in the animal kingdom. Instead of a typical snout, the developing birds were formed with mouthpieces much like velociraptors.
At the end of the age of dinosaurs more than 65 million years ago, an asteroid the size of Mount Everest struck the Earth, resulting in fires around the globe and a massive plume of black smoke that blocked sunlight for years. Many species went extinct, but some avian dinosaurs survived the catastrophe, later evolving into the myriad of bird species we see around us today.
"There are between 10,000 and 20,000 species of birds alive today, at least twice as many as the total number of mammal species, and so in many ways it is still the Age of Dinosaurs," said Bhart-Anjan Bhullar, a paleontologist and developmental biologist at Yale University and lead author on the study.
Beaks are one of the most important - and distinctive - parts of the anatomy of avians, including birds and some dinosaurs. The appendage is used for feeding, grasping items, and for self-defense, among other tasks. Biologists have long sought to understand how the specialized body parts evolved in dinosaurs and birds.
Researchers involved in the new investigation examined fossil records as well as the physiological makeup of modern-day animals, in order to develop a theory on the evolution of beaks. They then predicted which gene mutations would be required for those changes to take place, and searched DNA for evidence of these genetic changes. The team examined the genetic codes of alligators, lizards, turtles, and emus in the quest to confirm - or deny - their theory.
They found that one gene expression differs between all contemporary birds and nonavians, such as mammals and reptiles. This segment of genetic code triggers the development of beaks early in the formation of bird embryos.
Researchers used chemicals to inhibit the development of modern bird beaks in the developing creature. This resulted in the ancient code taking over the job of directing proteins, leading to the rise of an ancient beak. Unexpectedly, these ancient genetic instructions also affected the palatine bone on the roof of the mouth to revert to the design used by some dinosaurs.
Investigators hope their research techniques can be used by other biologists to better understand evolution through genetic modifications.
"Our goal here was to understand the molecular underpinnings of an important evolutionary transition, not to create a 'dino-chicken' simply for the sake of it," Bhullar said.
Development of dinosaur-beaked chickens was detailed in the journal Evolution.
