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CNN: how first birds flew



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Scientists Discover how First Birds Flew
Reuters            05-MAY-99

 LONDON, May 5 (Reuters) - The earliest known birds learned to fly by
running fast and flapping their wings, not leaping from tall trees,
researchers said on Wednesday. 

Exactly how birds began to fly has been hotly debated by scientists
since the 1800s. Most agree that birds evolved from dinosaurs, but how
they took to the skies has been a mystery. 

Critics of the running theory argued that early birds could not have
gained enough speed to build up the velocity to become airborne by
flapping their wings. 

But palaeontologists at The Natural History Museum of Los Angeles County
used aerodynamic calculations and fossil records to show that the oldest
known bird, the 150-million-year-old Archaeopteryx, was quick enough to
get a running start. 

"We went back and analysed previous ideas about how Archaeopteryx could
have flown," Dr Luis Chiappe said in a statement. 

"We discovered that some important aerodynamic issues had been
overlooked and that when these were considered, Archaeopteryx could
indeed run fast enough to achieve the necessary speed to take off from
the ground." 

Chiappe and his colleague Dr Phillip Burgers, whose research is
published in the science journal Nature, showed Archaeopteryx reached
its minimum flying speed by means of the thrust and residual lift
produced by flapping its wings. 

 "We regard thrust, and not lift, as the primordial force ultimately
responsible for sustained flight," the researchers said in the Nature
paper. 

 In addition to explaining how early birds achieved liftoff, the
research also shed new light on how winged but flightless dinosaurs
recently unearthed in China may have lived. 

 "The importance of this study," said Chiappe "is that this conceptual
theory can be applied not only to Archaeopteryx, but to their immediate
dinosaur ancestors." 

As a flier Archaeopteryx probably represents a late stage in the
evolution of bird flight. Chiappe and Burgers think early winged
dinosaurs were able to run faster and evade predators by flapping their
wings. Their descendents probably kept going faster and faster and
eventually were able to take off. 

Copyright 1999 Reuters Limited.All rights reserved. 
-- 
Flying Goat Graphics
http://www.flyinggoat.com
(Society of Vertebrate Paleontology member)
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