Although dinosaurs were wiped off of the Earth 65 million years ago, we still have dinosaur descendants roaming our planet in the form of modern-day birds. Now, using this evolutionary relationship, scientists have brought back a piece of dinosaurs in a study that led to the successful growth of dinosaur legs in chicken embryos.
"The experiments are focused on single traits to test specific hypotheses," said Alexander Vargas of the University of Chile, a member of the research team. "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."
Attempting to "bring dinosaurs back" is nothing new in the realm of scientific research. Over the past few years, various teams have been using a method called atavism activation in order to modify animals to express genetic ancestral traits; one grew a dinosaur "beak" on a chicken, and paleontologist Jack Horner proposed the creation of a "chickenosaurus" through the genetic modification of birds.
In the current study, the team focused on the dinosaurs' leg bones, noticing that avian dinosaurs such as the Archaeopteryx had long leg bones that, over the course of evolution, became shorter and shorter due to the decrease in length of the fibula.
After pinpointing that specific genes were actively preventing leg growth during development, the team turned off the expression of the maturation gene Indian Hedgehog, allowing the chickens' fibula to grow to a length that matched their tibia, reaching all the way to the ankle and mirroring the growth of a dinosaur leg.
One interesting observation that the team made was that in the experimental chickens, the tibia was significantly shorter, suggesting that a dinosaur-like fibula connecting to the ankle prevents the tibia from outgrowing it. The team tested this theory by looking at the fossil record and found that its suggestion was consistent with the evolutionary pattern it observed.
Although the results are still far from bringing back dinosaurs and the embryos never reached the hatching stage, the findings still provide insight into the evolution of dinosaurs into modern birds, and scientists hope that further research will increase our knowledge of this process.
The findings were published in the March 4 issue of Evolution.
