A few genetic tweaks recently gave some chicken embryos a facial makeover — they grew dino-like snouts rather than bird-like beaks, reports Ewen Callaway for Nature. The research effort isn’t part of a scheme to help dinosaurs walk the planet again, but rather one way that scientists are hoping to better understand how the "fearfully-great lizards" evolved into the smaller winged creatures birds are today.
The transition from dinosaur to bird was messy — no specific anatomical features distinguished the first birds from their meat-eating dinosaur ancestors. But in the early stages of bird evolution, the twin bones that formed the snout in dinosaurs and reptiles — called the premaxilla — grew longer and joined together to produce what is now the beak.
“Instead of two little bones on the sides of snout, like all other vertebrates, it was fused into a single structure,” says Bhart-Anjan Bhullar, a paleontologist now at the University of Chicago in Illinois and the co-leader of the new research.
Together with fossil evidence, living birds offer some of the best clues researchers have on how dinosaurs may have lived, moved, eaten and raised their young. The snout to beak transition is one of the most radically different parts of the avian skeleton, Bhullar told Melissa Hogenboom for BBC’s "Earth blog."
But first, the researchers had to figure out what a beak really is. The team looked at embryonic beak development in chickens and emus, and snout development in alligators, lizards and turtles. They spotted two proteins that direct the development of the face in these critters. However, in reptiles the two proteins, called FGF and Wnt, acted on two small parts of the embryonic face. In birds, the proteins were activated in a large band of tissue in the same area.
So all the researchers needed to do to test if that difference in protein activity was truly key in beak development was to block the wide band and restrict the proteins to the two spots they saw in reptiles. The chicks never hatched — the researchers were not trying to really create dino-chicken hybrids — but the difference was apparent. A flap of skin covered the chicks’ beak area, but underneath, they had shorter, rounder bones than the long, fused beaks of birds.
The researchers published their results in the journal Evolution. Their findings indicate that beaks are shaped by evolution because of the very different development cues they need. "That's what proves the beak is a real adaptation or 'thing', not just a slightly different nose shape," Michael Benton of Bristol University in the UK, who was not involved in the study, told told Hogenboom at the BBC.
Even though the birds never hatched, Bhullar says that he expects they would have survived. "These weren't drastic modifications," he told Hogenboom. "They are far less weird than many breeds of chicken developed by chicken hobbyists and breeders."
And they'll have to think hard before going further with attempts to turn back the bird-clock. "The rest of the animal looked OK, but one needs to think about this carefully from an ethical point of view."