Dinosaurs before birds. Re-engineering with alligator DNA, is that birds with a bite?:
Scientists re-engineer bird beak to ancestral “dino” state
Research aimed to retrace some of the evolutionary steps that gradually transformed dinosaurs into birds.
The research team, led by Yale University paleontologist and developmental biologist Bhart-Anjan S. Bhullar and Harvard University developmental biologist Arhat Abzhanov, used the fossil record as a guide. The scientists said they transformed chicken embryos into specimens with a snout and palate somewhat like that of small dinosaurs such as Velociraptor and Archaeopteryx.
The goal “was to understand the molecular underpinnings of an important evolutionary transition,” said Bhullar, lead author of the study, published online May 12 in the journal Evolution. “Little work has been done on what exactly a beak is, anatomically, and how it got that way.”
The scientists first analyzed the anatomy of related fossils and living animals to outline how the transition might have occurred. Next, they searched for possible shifts in gene activity, or gene “expression,” correlating with the transition. Finally they used chemicals known as small-molecule inhibitors to block the activity of presumed beak-specific genes.
This not only caused the beak to revert to an ancestral state—it had a similar effect on a bone at the roof of the mouth called the palatine bone, they said. This shows that “a single, simple developmental mechanism can have wide-ranging and unexpected effects,” Bhullar said.
The work took Bhullar from the alligator nests at Rockefeller Wildlife Refuge in southern Louisiana to an emu farm in Massachusetts. He extracted DNA from various species in order to clone fragments of genetic material to look for specific gene expression.
The research has several implications, Bhullar said. For example, if one molecular mechanism caused the transformation, there should be a corresponding change in the fossil record. The record bears that out so far, he argued. For example, an ancient relative of modern birds known as Hesperonis has both the modernized palatine bone and the modernized beak. The latter is visible in the so-called premaxillae—bones at the tip of the upper jaw, which in birds are enlarged and fused to form the beak.
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