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Scientists say they have reversed a bit of bird
evolution in the lab and re-created a dinosaurlike snout in developing chickens.
"In this work, we can clearly see
a comeback of the characteristics which we see in some of the first birds," says
Arhat Abzhanov, an
evolutionary biologist at Harvard University.
The ancestors of birds are a group of dinosaurs that
includes the famous velociraptor, Abzhanov says. This group of meat-eaters had
long snouts, small brains and eyes, and lots of teeth. Somehow they transformed
into birds, which have none of those things.
Bhart-Anjan Bhullar,
another member of the research team at Yale University, says the goal is to
understand exactly how birds became birds. "What's the deep history of
birdiness?" wonders Bhullar. "How did the different parts of their body plan
form?"
In particular, he and his colleagues are interested in
birds' distinctive beak, which Bhullar calls "this insane sort of snout that
they have."
To hunt for clues about the origin of the beak, the
researchers have been studying various kinds of animal embryos, from birds like
emus and chickens to nonbird reptiles like alligators, which are birds' closest
living relatives.
Their work led them to two specific genes. These genes
are active in the middle of the face-forming region of bird embryos, but not in
the middle of that region in the embryos of other animals.
Bhullar says he remembers the night he put the altered,
developing chicks under a microscope, and saw that they had unusual, broad
snouts.
"That was a pretty remarkable moment," he recalls.
"That's a moment that will stay with me, I think."
Instead of the normal bone structure that would form a
beak, he says, these protochickens had a pair of small, rounded bones that
looked "like those in a dinosaur, like archaeopteryx or velociraptor, or in any
other reptile — like an alligator."
A
report on the study
appears this week in the journal Evolution.
But don't expect the scientists to create lab-grown dinosaurs — that would be a
whole lot harder than just trying to restore some of the traits that existed in
the first birds.
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