It is well established that birds evolved from dinosaurs. However, over the course of that evolution there were some unusual twists and turns. There are, of course, the wings which are amazing on their own but nothing quite as unusual as a beak. Beaks are unique to bird species and there is a great deal of diversity among them. If you compare, for example, a hummingbird to an eagle or a woodpecker to a flamingo you’ll find a tremendous range of beak types, matched to the environment of its owner.
Researchers at Harvard and Yale wanted to understand the molecular process that transformed dinosaur snouts into beaks. The researchers used the fossil record as a guide, and collected DNA samples from a wide variety of birds and reptiles.
The researchers attempted to replicate and reverse molecular development in chicken embryos and created specimens with a palate and snout similar to dinosaurs such as Archaeopteryx and Velociraptor.
“Our goal here was to understand the molecular underpinnings of an important evolutionary transition, not to create a ‘dino-chicken’ simply for the sake of it,” said Bhart-Anjan S. Bhullar in a statement.
Bhullar is a Yale paleontologist and developmental biologist Bhart-Anjan S. Bhullar and lead author of the study, published online May 12 in the journal Evolution.
“The beak is a crucial part of the avian feeding apparatus, and is the component of the avian skeleton that has perhaps diversified most extensively and most radically — consider flamingos, parrots, hawks, pelicans, and hummingbirds, among others. Yet little work has been done on what exactly a beak is, anatomically, and how it got that way either evolutionarily or developmentally,” said Bhullar.
The scientists used “small-molecule inhibitors” to eliminate some of the bird specific molecules in the chicken embryos. By doing this they forced the ancestral ‘pre-bird’ activity to take place. According to the researchers, not only did the beak revert but the palatine bone on the roof of the mouth reverted as well.
“This was unexpected and demonstrates the way in which a single, simple developmental mechanism can have wide-ranging and unexpected effects,” said Bhullar.
According to Bhullar this implies that a single molecular mechanism caused the transformation and there should be, in the fossil record, a corresponding transformation. In other words there should be an animal that demonstrates the shift that lead from snout to beak.
“This is borne out by the fact that Hesperonis — discovered by Othniel Charles Marsh of the Yale Peabody Museum of Natural History — which is a near relative of modern birds that still retains teeth and the most primitive stem avian with a modernized beak in the form of fused, elongate premaxillae, also possesses a modern bird palatine bone,” he said.
According to Elizabeth Pennisi, staff writer with Science, however the research is somewhat controversial. Pennisi states that the finding contradicts an earlier study and that some scientists question the methods used.
Nathan Young and Ralph Marcucio of the University of California at San Francisco believe that the changes observed by the Harvard and Yale researchers could be a result of cell death caused by the inhibitor. The pair also believe that a different gene is responsible for the transformation.
