February 9, 2005 | David F. Coppedge

Octopus Arms Have Optimal Design

The tentacles of an octopus are soft and flexible, whereas bony creatures like us have joints that, while good for moving objects around, limit our freedom of movement.  Wouldn’t it be cool to have both?  An international team of neurobiologists, publishing in Nature,1 watched an octopus snare its food, using the flexibility of its tentacles, as expected.  But then they noticed, when it needed to transfer its prey from one place to another, it employed a “vertebrate-like strategy, temporarily reconfiguring its arm into a stiffened, articulated, quasi-jointed structure.”
    This gave them an idea.  Maybe the octopus has hit on something.  While the flexible arm provides a benefit for snaring objects, “an articulated limb may provide an optimal solution for achieving precise, point-to-point movements,” they wrote (emphasis added in all quotes).  National Geographic News adds, “scientists studying octopus arms conclude that they may represent the optimal design for robotic arms.”  Maybe the next-generation robotic arm on the Space Shuttle will resemble something from the ocean depths.  One researcher remarked that a stiff arm would be likely to push a floating object away, but “an arm you could use to gently wrap around an object and retrieve it, that would be useful.”  How to build such a device is the challenge.

1Sumbre et al., “Neurobiology: Motor control of flexible octopus arms,” Nature 433, 595 – 596 (10 February 2005); doi:10.1038/433595a.

Copying animal designs – biomimetics – is one of the hottest topics in engineering, for good reason.  Here is a creature that has the capabilities of a comic book superhero.  Sadly, both articles attribute this feat to evolution: “octopuses have evolved the optimal design,” says National Geographic, and the neurobiologists say in a wordier way,

Fetching seems to be an example of evolutionary selection of solutions that are similar even though they are based on quite different mechanisms – on morphology in arthropod and vertebrate limbs, and on stereotypical motor control in the octopus.  This functional convergence suggests that a kinematically constrained, articulated limb with two segments of almost equal length is the optimal design for accurately moving an object from one point to another.

This illustrates again how many countless times the scientific community and news outlets merely assume evolution is capable of any miracle needed, without telling us how the blind forces of nature could ever produce engineering design that humbles our best robotics experts.
    Some amazing footage of a particular octopus that can mimic many other animals can be found in a recorded lecture by Carl Kerby, “What is the best evidence God created?”, available on DVD from the Answers in Genesis bookstore.  The new film Incredible Creatures that Defy Evolution III has startling footage of a similar marine creature, the cuttlefish, with some other fantastic capabilities.

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Categories: Physics

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