Luis Rey, Wikimedia Commons
This is an illustration of Tyrannosaurus rex next to a chicken.
Chicken embryos that have legs nearly identical to those of prehistoric extinct dinosaurs were created recently by inhibiting the activity of a single gene.
The success of the project, outlined in the journal Evolution, brings scientists a step closer to creating “Dino-Chicken,” a chicken fully reverted to one of its dinosaur ancestors.
But the real application of having the DNA would be to learn all that we can about dinosaurs. DNA reveals so much: about ancestry, coloration, lifespan, gender, diseases, weight, behavior and much more. It would enable us to understand dinosaurs as fleshed out, complete animals instead of as a set of bones stacked up in a museum.
It would also enable us to better understand living dinosaurs (birds), shedding more light on why they survived the mass extinction event about 65 million years ago, while so many other animals didn't.
“The experiments are focused on single traits, to test specific hypotheses,” senior author Alexander Vargas of the University of Chile’s Department of Biology explained in a press release.
The scientists wanted to explore how the drumstick, or lower leg bone, of modern birds evolved. In extinct dinosaurs, the comparable bone — called the fibula — is tube shaped and reaches all the way down to the ankle.
In the evolution from dinosaurs to birds, the fibula lost its lower end and no longer connects to the ankle. It’s also is shorter than the other bone in the lower leg, the tibia.
Several decades ago, scientists noted that bird embryos develope a tubular, dinosaur-resembling fibula. Only as the embryo continues to grow does this leg bone become shorter than the tibia and acquire its adult drumstick shape.
Vargas and his team suspected that if they inhibited a single bird bone maturation gene, called Indian Hedgehog (IHH), they would wind up with modern birds essentially sporting dinosaur legs. They did just that in chickens and, sure enough, managed to create birds that had the leg bones of a dinosaur. Just like dinos, the fibula in the lab-grown chickens connected to the ankle.
You can see what those bone changes looked like in the figures published in the paper.
The experiment suggests that over time, the fibula lost its lower end, which likely allowed for the evolution of tibias that are much longer. The latter bears much of the body’s weight and plays an essential role in movement and locomotion.
The study is not the first time that lead author Joâo Botelho and his colleagues have caused chickens to de-evolve an ancestral dinosaur feature. Previously, they managed to undo the evolution of the perching toe of today’s birds. This resulted in a non-twisted, non-opposed toe, as seen in the remains of extinct dinosaurs.
Yet another research team, based at Yale, also altered gene expression in chickens. This resulted in chickens with a dinosaur-like snout.
None of those experiments have hatched out chicks with dino features, but eventually, a Dino-Chicken, aka Chickenosaurus, will likely be unveiled by “Jurassic Park” dinosaur expert Jack Horner.
For now, however, scientists are more focused on unraveling dinosaur-to-bird evolution, step by step.
As Vargas said: “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.”