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Desert Diary

Birds/Bird Fingers


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Is that symbol of the desert, the roadrunner, really a dinosaur? Depends on whom you ask. Most paleontologists think so, but not all. In part, it's a matter of fingers. Those dinosaurs thought to have given rise to birds have three fingers, and all agree that these are digits 1, 2, and 3; that fingers 4 and 5 have been lost evolutionarily. But scientists studying the embryonic development of birds have generally concluded that the fingers of birds are digits 2, 3, and 4, with the first and fifth having been lost.

Recently, biologists working with mice found that development of the thumb depends on a single gene, but the other fingers require both that gene and another one. Likewise, the first finger of birds needed the first gene only. They concluded that birds have fingers 1, 2, and 3. Solved? Well, others note that the roles of those genes in other animals aren't so clear-cut, and additional new evidence supports bird fingers as 2, 3, and 4. Sometimes, it's just hard to put your finger on conclusive evidence.

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Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.

Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.