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The Octopus Knot: Why Not?

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Did you ever wonder how an octopus keeps from tying itself in knots? Fortunately, we have an evolutionary biologist to explain it to us. Guy Levy, a doctoral candidate at Hebrew University in Jerusalem waves his arms and says that "evolution found" a "simple solution" to a nearly "impossible-to-solve problem." Live Science applauds and moves on to the next wondrous accomplishment of unguided evolution.

Those not satisfied with Darwinism as a catchall explanation for everything may wish to look deeper.

With eight arms moving about in all directions, it does seem the octopus is a Gordian knot waiting to happen. Each limb has seemingly infinite freedom. Now multiply that by eight! The limbs, moreover, can move independently of the brain, and are loaded with hundreds of suckers that tend to cling to almost anything they touch. Even amputated limbs can continue to move and grasp prey (octopuses lose limbs frequently, but fortunately for them, can grow them back). Previous experiments have also shown that the octopus is not really "aware" of its arms. How does an arm not wind up inserting itself into its owner’s beak?

The octopus gets along well without tangling up or eating its limbs. How? It has several built-in mechanisms. One is a behavioral program, sent from the brain to the limbs, that restricts the limbs’ freedom. This program also makes an octopus avoid grasping itself. Another is the ability to distinguish self from non-self. A third is a chemical secretion in its limbs that prevents sticking to its own skin. Levy and his colleagues found out that the secretions work with the self-recognition program, so that a limb is more likely to grab another octopus’s arms than its own, even if presented with an amputated or "zombie" arm.

Science Magazine summarizes the work performed in Israel:

Petri dishes coated with intact octopus skin became "immune" to the zombie arms. The same occurred if the skin was ground up into a mush and spread over the petri dish, implying that a special substance in the skin is responsible for repelling the suckers. That’s important because octopuses have been known to dine on their comrades. So somehow a chemical in their skin not only keeps them from tangling themselves up, but it also prevents them from eating themselves alive. (Emphasis added.)

Will the original paper in Current Biology explain how Darwinian evolution did it? On the contrary; the abstract sounds like this is a case for intelligent design:

Here we report of a self-recognition mechanism that has a novel role in motor control, restraining the arms from interfering with each other. We show that the suckers of amputated arms never attach to octopus skin because a chemical in the skin inhibits the attachment reflex of the suckers. The peripheral mechanism appears to be overridden by central control because, in contrast to amputated arms, behaving octopuses sometime grab amputated arms. Surprisingly, octopuses seem to identify their own amputated arms, as they treat arms of other octopuses like food more often than their own. This self-recognition mechanism is a novel peripheral component in the embodied organization of the adaptive interactions between the octopus’s brain, body, and environment. (Italics in original.)

We hunt for the word "evolution" in the paper, and find it right near the end. Just like in Live Science, though, Levy and his team use "evolution" as a catchall explanation for amazing properties that would otherwise be understood as products of intelligent design:

Finally, the mechanism of self-recognition fits well with the embodiment concept that explains why this and previous studies have revealed so many "surprises" in the octopus motor control system. The concept of embodied organization, proposed as a tool for designing autonomous robots, is that adaptive behavior emerges from the reciprocal and dynamic interactions of sensory and physical information among body, controller, and environment. In this form of organization, in contrast to hierarchical organization, the system functions as a whole, as it allows self-organizational processes to set the relevant dynamic properties of the elements building up the system — the embodiment. In robotics, this approach has led to the emergence of adaptive behavior by a robot in a specific environment.

As explained previously, studies on octopus motor control suggest that the concept of embodied organization may also be useful for biological systems. Crucial attributes of octopus embodiment are the morphology and the physical properties with which the octopus interacts with its environment. The morphology and flexibility of the octopus body are so unusual that almost every level of their motor system organization, from the higher motor control centers, to the autonomy of the elaborated peripheral nervous system of the arms, down to the neuromuscular system of the arms, have evolved special properties. This multilevel uniqueness is best explained by embodied organizationcoevolution of all the octopus systems to cope collectively with the complex motor control and behavior of this morphologically special animal. (Italics in original.)

Has the team really explained the octopus by evolution? Of course not. They identified multiple complex parts working together: a motor control system, sensory systems, motor control systems, peripheral nervous system, neuromuscular systems in the arms, programmed behaviors, and physical properties that interact with the environment. When you add designs together, you get design — even if the designs begin to interact with "embodied organization" in unanticipated ways (to human eyes, that is). Self-organization, even if that were what they were proposing as a theory, is not evolution in the Darwinian sense. "Embodied organization" is a hallmark of intelligent design. It implies that the whole body contributes to the function.

Indeed, the octopus design is so good, they want to copy it.

The results of the current study introduce a novel player into these dynamic interactions — a peripheral self-recognition mechanism that constrains interactions between arms. Such a mechanism is mostly advantageous in the control of flexible embodiments, where body parts can easily interfere with one another. Peripheral self-avoidance is a striking addition to the list of surprises in the motor system of this uniquely embodied animal.

From Live Science:

The findings could inform the engineering of nature-inspired robots, Levy added.

If any engineers among our readers are informed by blind, unguided processes, let us know. Most engineers, one assumes, apply their minds logically and intelligently to their robot creations, including after being inspired by the "embodied organization" of the octopus. If they can get their robot to mimic other animals, blend in with its environment, and make copies of itself, they will likely qualify for a Nobel Prize, not a Darwin Award.

Photo credit: Joe Parks/Flickr.


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