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"Bad Design" Debunked in a Fish: It Actually Achieves the Impossible

glass knifefish.jpg

An article on the Hub news page for Johns Hopkins University starts with a photo of a colorful glass knifefish, then poses a puzzle:

A quirk of nature has long baffled biologists: Why do animals push in directions that don't point toward their goal, like the side-to-side sashaying of a running lizard or cockroach? An engineer building a robot would likely avoid these movements because they seem wasteful. So why do animals behave this way? (Emphasis added.)

Stop right there. Ask how evolutionists and ID advocates would respond to this mystery. Evolutionists might think this is just leftovers from evolutionary "tinkering" or "cobbling," producing function good enough to permit survival. ID advocates might suspect a shrewder design than first meets the eye.

So what did the Johns Hopkins researchers learn from studying the apparently wasteful motions of the glass knifefish? In fact, they uncovered a superior design -- so good that it produces a functional benefit that has long challenged engineering wisdom:

A multi-institutional research team, led by Johns Hopkins engineers, says it has solved this puzzle. In an article published in the Nov. 4-8 online edition of Proceedings of the National Academy of Sciences (PNAS), the team reported that these extra forces are not wasteful after all: they allow animals to increase both stability and maneuverability, a feat that is often described as impossible in engineering textbooks.

Bad design achieves the impossible! What a surprise turnaround. You notice they didn't just talk about fish. This appears to be a general principle in organisms as diverse as fish, reptiles, honeybees and birds -- animals whose modes of locomotion can't be explained by evolutionary descent.

"One of the things they teach you in engineering is that you can't have both stability and maneuverability at the same time," remarks Noah Cowen, an associate professor of mechanical engineering at the university. There's a tradeoff; you either get one or the other. The Wright brothers faced this problem. It's been textbook wisdom, until now.

When an animal or vehicle is stable, it resists changes in direction. On the other hand, if it is maneuverable, it has the ability to quickly change course. Generally, engineers assume that a system can rely on one property or the other -- but not both. Yet some animals seem to produce an exception to the rule. "Animals are a lot more clever with their mechanics than we often realize," Cowan said. "By using just a little extra energy to control the opposing forces they create during those small shifts in direction, animals seem to increase both stability and maneuverability when they swim, run or fly."

An accompanying video shows how this works in the glass knifefish. The ventral fin produces waves that run in opposite directions. Intuitively, this looks wasteful. Don't the waves cancel out? Don't they waste energy? It turns out that by controlling the nodal point of where the waves meet, the fish can maneuver forward or backward with less energy overall.

This finding motivated more science. The researchers made a mathematical model of the motion, then they built a submarine robot to mimic the fish fin's action. Sure enough, the robot was more maneuverable and stable at the same time, requiring less control to move in various directions. Look in the abstract of the PNAS paper at how much science this generated:

Our results and analyses, which include kinematic data from the fish, a mathematical model of its swimming dynamics, and experiments with a biomimetic robot, demonstrate that the production and differential control of mutually opposing forces is a strategy that generates passive stabilization while simultaneously enhancing maneuverability. Mutually opposing forces during locomotion are widespread across animal taxa, and these results indicate that such forces can eliminate the tradeoff between stability and maneuverability, thereby simplifying neural control.

The paper elaborates on this latter point with more design words, like tuning and control:

Mounting evidence suggests that the passive design of animal morphology facilitates control, thereby reducing the number of parameters that must be managed by the nervous system .... the dynamic design of animal morphology and its attendant neural systems are tuned for simplified task-level control."

This pure science is also motivating applied science:

Cowan said this discovery could help engineers simplify and enhance the designs and control systems for small robots that fly, swim, or move on mechanical legs.

The research was valuable enough to be supported by three grants from the National Science Foundation and another grant from the Office of Naval Research.


Notice how the recognition of good design hiding behind apparent bad design is what moved science forward. Cowan and his colleague Malcolm MacIver recognized that engineering progress had actually been hindered by wrong assumptions:

"We are far from duplicating the agility of animals with our most advanced robots," MacIver said. "One exciting implication of this work is that we might be held back in making more agile machines by our assumption that it's wasteful or useless to have forces in directions other than the one we are trying to move in. It turns out to be key to improved agility and stability."

The assumption that biological design is "wasteful or useless" comes right out of Darwinian thinking. The principle that "if something works, it's not happening by accident" comes right out of design thinking.

The article and the paper say nothing about evolution, but even if these scientists are Darwinian evolutionists (we don't know), even if they did not mention the phrase "intelligent design" in the paper or publicity material, it is clear that design thinking is the hero of the story. The NSF and U.S. Navy funded what amounts to de facto ID science, just like the NSF did for Dr. Amy Lang and her butterflies.

Now, biologists can revisit the motions of everything from lizards to honeybees to hummingbirds with a new appreciation of their design. Cowan believes the newly discovered "design principle" will have wide application in mechanical devices. He's caught the inspiration of nature, so more is sure to come: "As an engineer, I think about animals as incredible, living robots."

Image: Glass knifefish; rok1966/Flickr.