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NYTimes.com Article: On Evolution and Growth, Clues From Birds' Beaks

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On Evolution and Growth, Clues From Birds' Beaks

January 24, 2003


Using tiny needles to exchange cells in 36-hour-old bird
embryos, scientists have replaced a duck's flat bill with a
quail's pointed beak, and vice versa. The experiment has
uncovered critical factors in the evolution of birds and
may lead to a better understanding of what causes human
facial birth defects like cleft palate. 

No matter what the species, beaks derive from
similar-looking embryonic tissue. To find out what makes
them turn out so different, researchers at the University
of California at San Francisco switched the neural crest
cells - the cells that give rise to beaks - in the duck and
quail embryos. 

They let the eggs incubate until they were about 11 days
old, halfway to hatching and large enough to tell what the
forming birds' beaks looked like. 

The ducks grew quail beaks and the quails grew duck bills,
the researchers report today in the journal Science. In an
accompanying review, Dr. Paul A. Trainor of the Stowers
Institute for Medical Research in Kansas City says the
experiments demonstrate that different species' neural
crest cells carry different programs for beak development. 

The transplanted cells also altered the way the birds'
natural tissues and even their genes reacted in the
presence of the foreign beak, slightly modifying some
surrounding facial features and speeding some gene action,
Dr. Trainor notes. Together, these factors make the cells
crucial to beak evolution. 

Dr. Jill A. Helms, an orthopedics researcher who is an
author of the new study, said an understanding of beak
development could shed light on human craniofacial
development. If people have an equivalent to the birds'
powerful neural crest cells, surgeons might someday be able
to correct a cleft palate before birth with a transplant of
mouth-growing cells.


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