Scientists Find Chickens Retain Ancient Ability to Grow Teeth

Feb. 27, 2006 — -- Chickens are in the news yet again, although not for the reasons one might suspect.

Scientists from the universities of Wisconsin-Madison and Manchester, U.K., have reason to rejoice after a successful experiment, which caused hens to grow conical, saber-shaped teeth.

This curious experiment was carried out by researchers studying the ancestry of birds and their evolution from flying, nonavian reptiles to the feathered creatures we now know.

"I was looking for feathers on the head of a mutant chicken embryo, and I noticed these formations along the edge of the beak that looked like alligator teeth," said lead researcher Matthew Harris, who specializes in the study of evolution and development.

The mutant chicken embryos that Harris studied possess a recessive and lethal trait called talpid2. As embryos, they can survive in eggs for as long as 18 days, but they never make it to the hatching stage (chickens normally hatch after 21 days). During their incubation, these mutant embryos begin to grow nascent teeth, like those found in ancient bird fossils.

When Harris and his colleagues "turned on" the talpid2 gene in the oral cavity of a normal chicken embryo, they found that the mutation caused the tissues in the embryo's jaw to initiate the formation of teeth, very much like those belonging to the bird's ancestors.

What makes this experiment unique is the fact that, unlike earlier experiments, it involved no grafting or tissue transplants from a mutant chicken.

John Fallon of the University of Wisconsin, who oversaw the project, said "These results provide clear evidence that these chickens possess the memory of the past; they have retained the ability to make teeth, under certain conditions. What I am describing is evolution."

Fallon's specialty is developmental biology, particularly vertebrate limb development and pattern formation.

The scientists discounted the possibility of this experiment having any direct medical application (to stimulate tooth regrowth in humans, for example). But they insisted on its importance to the human understanding of evolution, with Harris arguing that "the results of this experiment hit home, highlighting the potential in our genes to re-form what once existed.