A team of scientists are saying that in their bid of going back to the evolutionary steps which slowly has transformed dinosaurs into birds, they have successfully re-engineered embryonic chickens to grow snouts similar to that of dinosaurs.
The molecular process behind that shift has been replicated by blocking the activity of the relatively modern genes which control the beak development. This process has also facilitated them to outline a framework for studying other evolutionary transitions in a similar method.
The fossil record has been used as a guide by the research team led by Yale University paleontologist and developmental biologist Bhart-Anjan S. Bhullar and Harvard University developmental biologist Arhat Abzhanov. They have said to have transformed chicken embryos into specimens with a snout and palate similar to small dinosaurs such as Velociraptor and Archaeopteryx.
Bullar, the lead author of the study, published online on May 12th in the journal Evolution said, the goal “was to understand the molecular underpinnings of an important evolutionary transition. Little work has been done on what exactly a beak is, anatomically, and how it got that way.”
Firstly the anatomy of the related fossils and living animals had been analyzed for outlining how the transition might have occurred. Then they searched for possible shifts in gene activity or gene “expression” in correlation with the transition. Finally they have made use of chemicals known as small-molecule inhibitors for blocking the activity of alleged beak-specific genes.
Not only has this caused the beak to revert to an ancestral state, but it also had a similar effect on a bone at top of the mouth known as the palatine bone. According to Bhullar this shows that “a single, simple developmental mechanism can have wide-ranging and unexpected effects.”
This research has taken Bhullar from the alligator nests at Rockefeller Wildlife Refuge in southern Louisiana to an emu farm in Massachusetts. DNA from a variety of species has been extracted for cloning fragments of genetic material to look for specific gene expression.
Bhullar said the research has several implications such as if a single molecular mechanism was responsible for this transformation, there should be a corresponding, linked transformation in the fossil record. He said, “This is borne out by the fact that Hesperornis — 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.”
Premaxillae are the small bones at the tip of the upper jaw of most animals, but are enlarged and fused to form the beak of birds.
Bhullar also said that this same approach could be used to investigate the underlying developmental mechanisms of a host of great evolutionary transformations.
The other corresponding authors are Zachary Morris, Elizabeth Sefton, Bumjin Namkoong, and Jasmin Camacho, all of Harvard; Atalay Tok, of Uppsala University; Masayoshi Tokita, of Toho University; and David Burnham, of the University of Kansas.
