The period of the dinosaurs came to an end 66 million years ago, when a massive asteroid strike expedited their demise. However, not all of them died out; those that survived evolved into today’s birds.
Scientists are still trying to meticulously map out the anatomical changes that happened between dinosaurs and birds during this time period, and there may be no better way to do it than to participate in some “reverse evolution.” With this in mind, a group of scientists created “dinosaur legs” in chicken embryos, as described in their work published in the journal Evolution.
Surprisingly, earlier research on coaxing chickens into “becoming” dinosaurs has previously occurred. A 2015 study shown that hens with embryonic development changes might have a dinosaur-like snout. A lower-tech research a year earlier revealed how a few carefully placed weights might make a chicken move like a Tyrannosaurus dinosaur.
This new study used chickens to unravel the mysteries of the creation of dinosaurian bones. In fact, they’re already veterans of reverse evolution: The researchers succeeded in getting hens to sprout dinosaur-like feet in 2015. This time, they were curious about how the leg bones develop.
Modern birds are the living ancestors of the Coelurosauria, a huge group of feathered, non-avian dinosaurs that includes Deinonychus, Tyrannosaurus, and Velociraptor. The most renowned example of the transition between the most ancient Coelurosauria and today’s birds, Archaeopteryx, had a tube-shaped bone called the fibula that stretched all the way down to the ankle.
Bird fibulae no longer reach the ankle and become increasingly splinter-like as they mature. This team of researchers from the University of Chile investigated the genetics of the chicken to see why this shift occurred. They observed that by suppressing the activity or “expression” of a gene known as Indian Hedgehog (or IHH), the lengthy, dinosaur-like fibulae continued to develop.
This indicates that modern hens’ fibulae are genetically restricted from expanding beyond a particular point. The authors of the study observe that this stunted growth appears to be governed by the calcaneum, a bone in the ankle. The calcaneum determines when the neighboring fibula should cease developing as it grows.
When IHH was turned off, another bone-growth-related gene called PthrP became considerably more active. This pushed the fibulae to continue developing until they connected to the ankles, which is similar to Archaeopteryx skeletal architecture.
Unfortunately, these dinosaur-like chicks were not permitted to hatch. Because they were not meant to become genuine dinosaur-like creatures for commercial or non-scientific purposes, any hopes of reverse evolving chickens into buyable Deinonychus pets may have to be put on wait for the time being.