The University of Chile Scientists has created a chicken embryo that developed dinosaur-like feet after genetic manipulation, highlighting the evolutionary link between dinosaurs and birds. “The result is a chicken embryo with dinosaur legs.” In dinosaurs – the ancestors of birds – fibula, one of the two long bones of the lower leg, is tube-shaped and reaches all the way down to the ankle.

The research shows that “by inhibiting early maturation of a leg of the chicken embryo, the leg reverts to the shape that dinosaurs’ legs had,” Alexander Vargas, one of the researchers, said. However, in the evolution from dinosaurs to birds, it lost its lower end, and no longer connects to the ankle, being shorter than the other bone in the lower leg, the tibia.

Scientists noted that bird embryos first develop a tubular, dinosaur-like fibula. Then, it becomes shorter than the tibia and acquires its adult, splinter-like shape. Theropods, a group of dinosaurs, started as carnivores but evolved to eat plants and insects. Birds evolved from small theropods in the Jurassic period more than 145 million years ago.

Brazilian researcher Joao Botelho, working in the lab of Alexander Vargas from the University of Chile studied the mechanisms that underlie this transformation. In normal bone development, the shaft matures and ceases growth long before the ends do.

In their study, scientists manipulated the Indian hedgehog homolog gene common to all animals, including man. They were trying to pinpoint when birds had a dinosaur-like fibula bone. When the researchers delayed early development, the bone took on the tubular shape it once had in dinosaurs.

Unlike other animals, the calcaneum in bird embryos presses against the lower end of the fibula. They are so close they have even been mistaken for a single element. Botelho proposes that at this stage, the lower end of the fibula receives signals more like those at the bone shaft. Working with Jingmai O’Connor from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in China, the research team realized this was consistent with an evolutionary pattern documented by the fossil record.