To make an omelet, you need to break some eggs. Not nearly so well known is that breaking eggs also can lead to new information about the evolution of birds and dinosaurs, a topic of hot debate among leading biologists.
Drs. Alan Feduccia and Julie Nowicki of the University of North Carolina at Chapel Hill have done just that. They opened a series of live ostrich eggs at various stages of development and found what they believe is proof that birds could not have descended from dinosaurs. They also discovered the first concrete evidence of a thumb in birds.
"Whatever the ancestor of birds was, it must have had five fingers, not the three-fingered hand of theropod dinosaurs," Feduccia said. "Scientists agree that dinosaurs developed hands with digits one, two and three -- which are the same as the thumb, index and middle fingers of humans -- because digits four and five remain as vestiges or tiny bumps on early dinosaur skeletons. Apparently many dinosaurs developed very specialized, almost unique hands for grasping and raking. "Our studies of ostrich embryos, however, showed conclusively that in birds, only digits two, three and four, which correspond to the human index, middle and ring fingers, develop, and we have pictures to prove it," said Feduccia, professor and former chair of biology at UNC. "This creates a new problem for those who insist that dinosaurs were ancestors of modern birds. How can a bird hand, for example, with digits two, three and four evolve from a dinosaur hand that has only digits one, two and three? That would be almost impossible."
Deb Saine | EurekAlert!
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