One of the biggest myths in science was that dinosaurs have been extinct for 65 million years. Thanks to new fossil discoveries, we now know that some dinosaurs went extinct after an asteroid collision with Earth, but others survived and gave rise to the birds we live with today.
Researchers in Chile carried out a strange experiment to figure out how this evolution happened. They manipulated the genes of regular chickens, causing them to develop fibulas on their lower legs, which are similar to a drumstick.
The fibula was a tube-shaped bone that reached all the way down to the ankle in dinosaurs. The tibia grew to the same length as the other bone.
The fibula became shorter and more splinter-like as evolution progressed through the Pygostylians, and it no longer reached the ankle.
The bones of modern bird embryos are shorter, thinner, and splinter like the Pygostylian bones, but they never make it far enough down to the leg to connect.
The transition from a long, tubular fibula in dinosaurs to a short, splinter-like fibula in birds was investigated by researchers.
The chickens were able to grow the long, dinosaur-like fibulae that originated in their embryonic form because of the inhibition of the expression of the IHH gene.
The team discovered something strange. Growth in the fibula stops first at the ends of the fibula in modern chickens, but in regular bone development, cell division stops before the ends stop growing.
The fibulae of modern chickens are not able to reach the lengths of their ancient relatives' bones.
Botelho et al. are part of the Evolution team.
The calcaneum, a bone in the ankle, is thought to be the reason for the early maturation of the lower end of the fibula in chickens.
The calcaneum in bird embryos presses against the lower end of the fibula. They have been mistaken for a single element by some researchers.
The team suggested that the calcaneum and the end of the fibula are similar to the ones that stop the bone shaft from growing.
The calcaneum strongly expresses the Parathyroid-relatedProtein (PthrP), which allows for growth at the ends of bones, when the Indian Hedgehog gene was turned off. The chickens grew long fibulae that connected with the ankle, just like they would in the Archaeopteryx.
The team wrote that the tibia and fibula were equal in length after the downregulation of IHH signaling. The fibula is longer than in controls and fused to the fibulare.
The purpose of the research was not to raise the 'dino-chickens' into adulthood but to figure out the biological processes that led to the transition from dinosaur legs to modern bird legs.
The team is focused on single traits to test hypotheses, and they know a lot about bird development and the dinosaur-bird transition. hypotheses on the evolution of development can be explored in the lab.
This isn't the first time dinosaur traits have been re-created in chickens. In 2015, the same team achieved the growth of dinosaur-like feet on their chickens, and a separate team in the US did the same.
Jack Horner, the lead researcher and renowned paleontologist, was able to do it.
The research was published in a book.
The first version of this article was published in March of 2016
