Machines and Information are Bad Metaphors in Biology

Continuing the discussion from The Flagellum is Not a Motor?:

On another thread, @T.j_Runyon points to an excellent article worth discussion in its own right. The history and perspective in this article is really good. I’m curious @TedDavis’s take on it too…

When delving into unknown territory, scientists have often naturally relied on their experiences in more familiar domains to make sense of what they encounter (De Cruz & De Smedt 2010).

In their classic work on metaphors, Lakoff and Johnson argue that the basic function of metaphorical concepts is to structure a new kind of experience in terms of a more familiar and delineated experience (Lakoff and Johnson 1980). In science as well as in everyday expression. language, metaphors highlight particular aspects of whatever it is we are trying to grasp, but they will inevitably distort others.

And that is my concern here. Analogies are how we reason about biology but all analogies are ultimately flawed. A core part of biological education is understanding where they break down.

As for the power and limits of analogies, see C.S. Lewis’s Bluspels and Flalansferes, which @jongarvey has written about…

And the idol of the marketplace, which continues to plague thinking about biology.

The limits of analogy are important, but in this specific context so is the full breadth of definitions. I concentrate here on “flagellum as motor.”

Etymologically, Latin “motor” means the one who moves something. Usually a person.

It’s fifty years since I did physics A-level, and though I still get regular dreams about being unprepared for the exam (never for zoology, for some reason) I did revise that in mechanics, a machine is defined as “a system using energy to perform work.”

Some of the simplest machines are inclined planes, levers and pulleys, and the laws of mechanics apply however the system is set up. Thus an inclined plane used to build the Great Pyramid is no more or less a machine than wind blowing sand up a sand-dune, and a falling tree dislodging a boulder is as truly a lever as Archimedes moving the earth with one. Similarly, the olecranon process of the elbow is a lever, even if it also performs other functions. No analogy, just application of mechanical definition.

“Motors” are the class of machines in which the form of work produced from energy is (primarily) motion. So they may be electric rotational motors, linear motors, clockwork mottors or rocket motors (with, at their simplest, no moving parts). They are motors if energy->system->kinetic work.

And that is why, when I studied physiology and anatomy, striated muscle consisted, functionally, of motor fibres, the muscle was supplied by motor neurones (hence “motor-neurone disease”), and those ended up in the motor cortex. No analogy - just a biological instantiation of mechanics.

It matters not that muscles are also used to generate heat (in shivering), sound (as in laryngeal folds) or whatever - any more than a siren ceases to be a motor because it has some extra device, or because it is also a gyroscope.

The only question, then, is whether the flagellar assembly converts energy to motion (of the flagellum, or of the cell). If it does, it is a motor. And it does, literally and not analogically. The comparison MUST be with the definition in mechanics, and not with some popular image of what a motor “ought” to be.

By all means, at that point question any claims to irreducible complexity, to design or whatever errors you believe the IDists make. But if you’re going to use Shannon Information theory, rather than a broader definition, to discount biological information, then to be consistent you should use the definition of “machine” or “motor” derived from mechanics to assess molecular machines or flagellar motors. I don’t see why there should be any dispute on those definitions.


Well of course the flagellum is a motor in that limited (I.e. broad sense). As I believe you are doing, we are just resisting missusing the analogy.

And the reason we are investing this sublime amount of energy to resist abusing analogies is because this is a toxic topic that cant be “put down”… like many ID threads.

ID-threads and Evolution-without-God threads should not dominate the discussions here. They should be entertained (or ignored, per personal preferences) by restricting them to a single folder for “Off-Topic” disputation.

Then EVERYONE gets what they want… as long as what they want is not the ability to disrupt and divert the entire list!

Why is this idea considered taboo?.. when virtually all Creationist forums dont even ALLOW disputing topics from the opposing audiences?

Which flagellum?

Since the definition of “motor” comes from mechanical physics, rather than biology, it is not relevant which type of flagellum is under consideration, provided that (a) it uses energy and (b) produces motion. If it does, then it meets the physical definition of “motor.”

Unless, of course, you know of a biological definition of motor that applies to only some types of flagellum? If there is one, nobody has offered it here, and mechanical theory is a better guide than someone’s arbitrary opinion on what constitutes an analogical motor.

@jongarvey, most people are not using the definition from mechanical physics, they are using the “ordinary” definitions. These definitions analogize between o “every day” objects, like the engine in our car, and less familiar things. For example, see what @bjmiller writes:

Notice several things that @bjmiller has added to the definition:

  1. Human-designed
  2. Outboard
  3. Rotary

First of all, the flagellum is not an outboard motor. It is not “outboard” in any meaningful sense, because it is not separable from the membrane. In fact it requires the membrane in order rotate, where an outboard motor is separable from the point at which is mounted, and is correspondingly more complex because it needs to be able to operate independently.

Second, it is not analogous to human-designed motors in several ways. Perhaps most importantly to this conversation, it works in a very different way, it is far more simple than a human-designed motor, and it is has a plausible evolutionary path. Likewise, no one thinks a human-designed motor can pop into existence without a human assembler, but everyone agrees that flagellum do not require intelligent assemblers. If a non intelligent force can assemble a flagellum, we are right to wonder if non-intelligent forces can evolve them.

Third, @bjmiller is neither using your definition of “motor,” nor is he using the definition from "mechanical physics. Fourth, you just switched your own definition from the early meaning (which would include our legs being motors for movement) to be the definition from mechanical physics. A flagellum is a motor by some definitions, but not by most definitions. It is only weakly analogous to a human-designed motor, and that is precisely where much of the confusion arises.

I’m fine with you using a reduced definition of motor and then using it consistently. It is a problem, however, if we start equivocating multiple definitions together, as is often happening here.

Equivocation between various members in an opposing dialogue is simply inevitable. Not even scientists within a single discipline can manage definitional purity. The whole Geneaological Adam insight arose by understanding this more clearly in the arena of human origins, @swamidass !
That’s why it’s important to be willing to hear one another, and to stop demonizing those who argue for more of what you want less of. Just the way the cookie crumbles for both sides. Perhaps we can benefit by arguing more along the lines of “how much, versus how little,” rather than “genius or stupid.” My two cents.

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The difference is that for scientific theories it doesn’t matter how pure your definitions are since scientific theories don’t depend on definitions. Language in science is used to get your ideas across to other scientists, and it is those ideas and observations that matter.

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Agreed. Good point. Definitions, however, can be tuned to serve that purpose better, but only through a process of gradual refinement within a like-minded community.
We might even have to admit that this is what’s being attempted here, rather contentiously. : )

Yes, like “evidence.”

Scientists are a very contentious bunch, but in a good way. There are scientists who like to make a name for themselves by inventing new vocabulary and definitions. Sometimes that is useful, but most of the time it isn’t. Get a bunch of biologists together and ask them if “metabolomics” is a useful term and you will get a wide spectrum of opinions.

Scientific jargon is a two edged sword, especially when it comes to communicating science to the general public. It allows for scientists to convey ideas to one another, but it can also be opaque to the general public, or even lead people to the wrong ideas. It is important for scientists to hone their communication skills, and also be careful not to mistake language for data. Being reminded of our fallibility is always a good thing.


As is being reminded of our common passion for ferreting out the truth about how things work. Agreement is also fun!
Will try to familiarize myself with the “metabolomics” controversy! ?
I’ll risk an idiosyncratic “definition” --the study of the ins and outs of cellular coprophagia? Could be totally off-base, though… : )

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OK, so finally a topic I have some relevant expertise in. My graduate work was on designing and interrogating (man made) molecular rotary motors.

A working definition we might use for rotary motors would look something like “unidirectional net motion of a rotor about an axis of a stator, that converts energy into mechanical work”. I think by that definition the flagellar motor is a rotary motor.

I seems like the battle is what a biological motor does for “design” arguments, etc. but my perspective, as a physical chemist who was involved in the design and analysis of molecular motors, is that there are clearly biological systems (including flagella) that meet common definitions of molecular motors.

I get where @swamidass is coming from, I can’t really see how molecular/biological motors can really help “design” arguments beyond the superficial hand-wavy type like:

  1. macro-scale motors (combustion engines, electric motors) are designed by humans
  2. biological motors are also motors
  3. therefore, molecular motors must be designed

But I don’t think the fault is in premise 2, the fault is that 3 doesn’t necessarily follow from 1 & 2.

I also think that argument does a discredit to nature (and the Creator, frankly) because natural systems are often way more complicated than man-made systems, and yet they work just fine without our “design” or intervention. Why should our conception of “design” be the arbiter of how God works through his creation?



The problem i had with the discussion is that some of us seemed fixated on the idea that a one celled creature could have an installed motor… but no equivalence was made to describing muscles in mammals as a kind of engine.

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