Evolution: development of flying not understood (Introduction)

by David Turell , Wednesday, August 03, 2022, 18:37 (842 days ago) @ David Turell

A new biomechanical study:

https://www.quantamagazine.org/geometric-analysis-reveals-how-birds-mastered-flight-202...

“Evolution has created a far more complicated flying device than we have ever been able to engineer,” said Samik Bhattacharya, an assistant professor in the experimental fluid mechanics lab at the University of Central Florida. The reasons why today’s aircraft can’t match avian maneuverability aren’t simply a matter of engineering. Although birds have been meticulously observed throughout history and have inspired designs for flying machines by Leonardo da Vinci and others through the centuries, the biomechanics that make birds’ maneuverability possible have largely been a mystery.

A landmark study published last March in Nature, however, has started to change that. For her doctoral research at the University of Michigan, Christina Harvey and her colleagues found that most birds can morph their wings mid-flight to flip back and forth between flying smoothly like a passenger plane and flying acrobatically like a fighter jet. Their work makes it clear that birds can completely alter both the aerodynamic characteristics that govern how air moves over their wings and the inertial characteristics of their bodies that determine how they tumble through the air to complete fast maneuvers.

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The 2001 research showed that inherent stability played a bigger part in the flight of birds than was generally believed.

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They wrote a novel modeling program that represented different types of wings, bones, muscles, skin and feathers as combinations of hundreds of geometric shapes. The software allowed them to calculate relevant characteristics such as the center of gravity and the “neutral point” that is the aerodynamic center of the bird in flight. They then determined those properties for each bird with its wings configured in a variety of shapes.

To quantify each bird’s stability and maneuverability, they calculated an aerodynamic factor called the static margin, the distance between its center of gravity and its neutral point relative to the dimensions of the wing. If a bird’s neutral point was behind its center of gravity, they considered the bird to be inherently stable, meaning that the flying bird would naturally return to its original flight path if pushed off balance. If the neutral point was in front of the center of gravity, then the bird was unstable and would be pushed further from the position it was in — which is exactly what must happen for a bird to be able to do a breathtaking maneuver.

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birds, unlike airplanes, can move their wings and shift their body postures, thereby altering their static margins. Harvey and her team therefore also evaluated how each birds’ inherent stability changed in different wing configurations.

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Four species were completely stable, and 17 species — including swifts and pigeons — could switch between stable and unstable flight by morphing their wings. “Really, what we’re seeing is these birds being able to shift between that kind of more fighter-jet-like style and a more passenger-jet-like style,” Harvey said.

Further mathematical modeling by her team suggested that rather than enhancing birds’ instability, evolution has been preserving their potential for both stability and instability. In all the studied birds, Harvey’s team found evidence that selection pressures were simultaneously maintaining static margins that enabled both. As a result, birds have the ability to shift from a stable mode to an unstable one and back, changing their flight properties as needed.

Comment: birds come with very specialized wing shape morphing abilities. When a young bird fledges, it is learning to use these provided abilities. Such complexity requires a knowledgeable designer. Current bird Flight is not just jumping into the air and a stepwise evolutionary development is not possible.