Flying Creatures: Created or Evolved?
- Tuesday, January 25, 2011
(Condensed and updated from his book By Design,* Chapter 4)
Humans achieved true powered and sustained flight only about one hundred years ago, after many laughable failures. Two Christian bicycle-making brothers, Wilbur and Orville Wright from Dayton, Ohio, carried out the first real flight at Kill Devil Hills near Kitty Hawk in North Carolina at 10:35 a.m. on 17 December 1903.1 Yet airplanes were not the first heavier-than-air fliers. Inventors learned much from hours of bird watching through binoculars. One vital secret they learned was that birds controlled their flight in three axes, which involves control of their wing shape. Thus, the Wright brothers developed a system to control the wing shape on their flying machines.
James DeLaurier, a professor emeritus at the University of Toronto who spent decades studying flapping wings, said: "It's respectable to look at nature for inspiration. We don't come close to doing all the things that nature does."
"It's absolutely good design if you copy nature," concurred Terry Weisshaar, an aeronautics professor at Purdue University. John McMasters, an aerodynamics expert at jet manufacturer Boeing, has taught aircraft design for forty years, and agreed: "One of the rules is never invent anything you don't have to. If you can find a precedent that solves a problem, use that." He added that lessons learned from nature will play an increasing role in new aircraft.2 As an example, "In the future, the swift's flight control might inspire a new generation of engineers to develop morphing microrobotic vehicles that can fly with the agility, efficiency, and short take-off and landing capabilities of insects and birds."3,4
Even before powered flight, pioneers in gliding learned from birds: "The gliding flight of storks inspired the first airplane designs of Otto Lilienthal in the late nineteenth century. The benevolent flight characteristics of these slow and stately gliders invested airplane pioneers with the confidence to take to the skies."4
If it took intelligence and planning to design an airplane, what does it say about the flying machines that the Wright brothers studied? And these can do something that airplanes can't—they can make copies of themselves!
How Do Birds Fly?
Since heavier-than-air machines must overcome gravity, they need some balancing upward force, which comes as a direct result of the special shape of their wings. Birds, and now airplanes, have wings shaped as aerofoils, so that as they move forward, air is deflected downward. This is because the wing is angled slightly upward ("angle of attack") and also because the air follows the curve on the upper surface (because of the "Coanda effect"), which points down. This downward airflow produces an upward force (lift) because of Newton's Third Law of motion,5 which was discovered by another creationist:6 every action has an equal and opposite reaction. You can feel this strong downdraught of air under a helicopter's rotor, which is essentially a rotating wing.
Airplanes need a motor to move forward, while in birds, this effect is produced by flapping. Birds' primary flight feathers are angled in such a way that they force air backward, so the bird is propelled forward, again in compliance with Newton's Third Law.
Special Features of Birds
When birds flap their wings, most of the resulting power is generated by the downstroke. But after the downstroke, something must raise the wing again for the next downstroke. Fortunately, birds have an intricate pulley system—the supracoracoideus muscle pulls on its tendon, which winds around a pulley comprising the coracoid and clavicle bones, then inserts into the humerus or upper arm/wing bone.
Birds can still fly if the tendon is cut, but takeoff is badly hindered when this situation occurs.7 So why would natural selection choose a half-formed pulley? Indeed, there is no evidence of transitional half-pulley systems in the fossil record, and would such a half-pulley be any use at all?8
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