Dinosaur Legs on Chicken Embryos Grown by Scientists for the First Time
A recent fossil discovery made by scientists brought forth a treasure of knowledge that busts one of the oldest scientific myths about extinction of dinosaurs. Unlike the common belief, not all dinosaurs perished with the asteroid collision. There were some that lived on to evolve into birds we see today.
Researchers from Universidad de Chile made a huge discovery when they revealed how the evolutionary changed happened over the years from a dinosaur to a bird. They used genetic modification on chicken embryos for the purpose of the study. In other words, the scientists grew a dinosaur leg, the first of its kind since in 65 million years!
The first avian dinosaurs, Archaeopteryx, had a tube shaped bone that reached down to the ankle. Tibia, another bone, grew next to it and had the similar length. However, over the course of evolution of avian dinosaurs, Pygostylians, the fibula grew shorter than tibia and sharpened towards the end, while no longer reaching the ankle. The embryos of modern day birds reveal signs of growing fibulae, like seen in a dinosaur. As they grow, the bones become thinner and shorter, while never reaching far down enough to connect leg with the ankle.
Researchers led by Joâo Botelho examine how this transition from dinosaur's long, tubular fibula happened to reach short, splinter-like fibula that we see in birds. For the purpose of their study, the researchers inhibited the expression of IHH (Indian Hedgehog) gene which led to their chickens develop long fibulae, like the one seen in dinosaurs, in their embryonic form.
The researchers published their study in the journal Evolution. They reveal that early growth of fibula's lower end in chickens today is caused by calcaneum, a bone in the ankle.
"Unlike other animals, the calcaneum in bird embryos presses against the lower end of the fibula," the team explains in a press release. "They are so close, they have even been mistaken for a single element by some researchers."
"The experiments are focused on single traits to test specific hypotheses. Not only do we know a great deal about bird development, but also about the dinosaur-bird transition, which is well-documented by the fossil record. This leads naturally to hypotheses on the evolution of development, that can be explored in the lab," said one of the team members, Alexander Vargas.
