Birds evolved from dinosaurs 150 million years ago, a slow but thorough transformation. Their bodies gained aerodynamic feathers, their digits fused into wings, and they acquired a beak used to gather food.
We can see some details of this evolutionary marvel in the fossil record. Yet even the most exquisitely preserved fossil can’t tell us which pieces of DNA had to change in order to turn ground-running dinosaurs into modern birds.
Some researchers are now trying to pinpoint those genetic changes with experiments on chicken embryos. If the scientists succeed, they should eventually be able to reverse the evolution of birds — and then they may be able to engineer animals more at home in “Jurassic Park” than in a henhouse.
One group of these scientists, led by Bhart-Anjan Bhullar of Yale University and Arhat Abzhanov of Harvard University, has spent the past eight years investigating one piece of bird anatomy in particular: the beak. Now, in a study published in the journal Evolution, they report that they have found a way to turn the beaks of chicken embryos back into dinosaur-like snouts.
In interviews, some experts hailed the new research for providing insights into the evolution of birds. But others were skeptical, arguing that the real genetic changes behind the bird beak have yet to be discovered.
The beak evolved fairly late in bird evolution, after early birds had already evolved feathers and powered flight. It originated from a pair of small, separate plates of bone sitting at the front of the upper jaw. In our own skulls, these bones — called premaxillae — anchor some front teeth.
During the evolution of early birds, the premaxillae stretched out and fused together to form a strong, lightweight beak. Muscles that anchored the new beak to the back of the head allowed birds to control this sophisticated tool.
Since then, birds have evolved many uses for beaks. Woodpeckers hammer into trees to find insects. Pelicans use their beaks like fishnets. Hummingbirds evolved slender sipping straws.
Dr. Bhullar and Dr. Abzhanov set out to find some of the genetic changes that turned the dinosaur premaxillae into a beak. To find clues, they looked at earlier experiments on chicken embryos. These studies have documented how embryonic cells make certain proteins at certain times.
The scientists were struck by the fact that even before the embryo has a developed, recognizable face, a large patch of cells in the middle of what will become the bird’s face makes a protein called Fgf8. Later, the region produces different proteins, called Lef1.
