Using chickens to reverse-engineer dinosaurs
Modern birds have changed in a number of ways since the Mesozoic era. Thanks to the slow process of evolution, birds’ genes have accumulated more and more differences from the last common ancestor they shared with other groups of theropods. Recent experiments have tried to identify the root of some of those changes in some chickens’ DNA, and then roll them back to their ancestral state.
The targeted structure was the chickens’ beaks. Most animals, including more closely related reptiles and non-avian dinosaurs, have a snout made of two symmetric bones, called the premaxilla. Modern bird beaks, however, are a single, hard bone, attaching on both sides of the skull. This difference was thought to be at least partially due to the expression of two proteins when the embryonic bird was growing. So these two proteins were suppressed to see if the fused beak could be undone.
Growing ancient anatomy
It more or less worked. The resulting embryos (no dinofied chicks were actually hatched) weren’t drastically different on the outside, but they did have a couple of key shifts more inline with dinosaur anatomy. The first was that the beak was not fused, revealing distinct premaxilla. The second change found was to the embryos’ palates, which had grown wider and more robust, resembling the palates found in early theropods’ mouths.
This doesn’t mean that we’re going to now immediately roll back millions of years of evolution and grow Tyrannosaurs from chicken eggs by blocking any gene less than 65 million years old. While two proteins made multiple differences in these bird skulls, there’s still a lot more to tackle if we’re to grow modern animals with ancestral structures (such as an ancient tail, which is being investigated already).
Source: 'Dino-chickens' reveal how the beak was born by Ewen Callaway, Nature