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Complexity is more
than Cilium, Flagellum ...


Short Answer:

The following highlights complexity and layering of complex and specified systems. All too often, those who favor evolution and proponents of design fail to fully express the dimensions (degree) of difficulty layered systems pose in relation to origins of life. One cannot simply look at one feature or system alone and say the probability is exceedingly low that chance events account for the origin, when in fact multiple systems are integrated with one and other ... probabilities factored atop other probabilities extrapolate from there. Just 'ordinary' features all combined make cell features and systems extra-ordinary.

A definition for irreducible complexity is:

An irreducibly complex system is one that requires several closely matched parts in order to function and where removal of one of the components effectively causes the system to cease functioning. Behe (MC) Page 178

If core components of a complex system (unique cell structure, signal system, metabolic pathway, etc) are all at once necessary for the system to function properly, then the "all-or-none" condition challenges the concept of a gradual stepwise appearance.

A Look From The Other Side

From another perspective, no logical progression of nonfunctional or non-beneficial intermediate stages makes for evolution. The basic evolutionary principle is all such ineffective intermediates would be eliminated by natural selection. In other words, the entire assembly of all parts must appear all at one time to confer function and benefit to an organism. All too often the assumption is "it exists therefore it evolved."

Irreducibly Complex Systems include:

1) certain sets or complexes of enzymes that make up a unique biochemical pathway (e.g. blood clotting cascade)

2) a fine structure element of a cell (e.g., flagellum, cilium, with numerous protein molecules compose the system)

3) other examples would qualify where a system is built with multiple core components and a loss of function results if even one part is missing. This not only applies to structures, but also to biological information (genetic, epigenetic, developmental sequences, and information within organelles). Think of all this like a machine that becomes useless because a gear is removed.

Energetics and Complexity:

Organisms gather resources, synthesize, and then expend energy, with considerable efficiency, to support their lives (and really this energetic efficiency extends to sustaining a species as a whole). Life's energetics systems run contrary to entropy in the universe! Energy expended to make or sustain an incomplete, ineffective, nonfunctional cellular component makes little sense—in biological and intellectual terms! Doing so degrades fitness and minimizes chances of survival. To suppose generation to generation life's partial features are sustained such that some day full functionality would be realized is not a topic taught in biology classes. Do parts of a sophisticated system 'know' to appear in advance of eventual full functionality? What sustains these parts until integrated into a full functionality? Why then— without evidence—would one assume such occurrences exist or are routine in nature?

figure 128

Implications from Complexity

Irreducibly complex systems in living cells provide examples for our consideration of the concept of intelligent design. A researcher can also look at such examples and 'test' or 'detect' the presence of 'specification,' which is characteristic of intelligent design. A tool that serves as a design detector is the 'explanatory filter.' And if complex examples reflect design, then there is more to consider than is expressed by assumptions made for biological evolution.

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Consider This:

Discussions on complexity in nature predate Darwin's theory. General examples for an "Argument from Design," like that put forth by William Paley's "Natural Theology," published in 1802 [link to entire publication in PDF], are subject to debate. But if moving forward in time, past Paley, past Darwin, well into the 21st Century, there are scientific advancements and far more sophisticated evidence that now enters a renewed view on design in nature. The modern day evidence begs a new look and different conclusions.

Only with the discovery of the molecular basis of life has science been able to address questions about life's basic mechanisms. Science has learned over the past four decades that the many cellular tasks required to sustain life are carried out by machines—literally, molecular machines.

In Darwin's Black Box I discussed several such machines. I showed that they are irreducibly complex—that is, they require a number of closely matched components before they can function—and thus are mammoth barriers to gradual, Darwinian evolution. I further argued that such irreducibly complex systems are best interpreted as the result of deliberate intelligent design. Behe (MC) Page 177

The evidence comes from biochemistry, biophysics, cell science, molecular genetics, and other areas of science. Technology—especially with post-World War II advancements—has revealed the inner workings of life previously unimagined.

... the appearance of design in at least one important domain of biology cannot be so easily dismissed. Since the late 1950s advances in molecular biology and biochemistry have revolutionized our understanding of the miniature world within the cell. Modern molecular biology has revealed that living cells—the fundamental units of life—possess the ability to store, edit and transmit information and to use information to regulate their most fundamental metabolic processes. Far from characterizing cells as simple "homogeneous globules of plasm," as did Ernst Haeckel (Haeckel 1905, 111) and other nineteenth century biologists, modern biologists now describe cells as, among other things, "distributive real-time computers" and complex information processing systems. Meyer (MC) Page 113

One way to look at complexity is to think of what minimal parts are needed ...thus "how simple" is the smallest possible cell. Even then, is it really so simple? At the minimum would be just the right systems with their core constituent parts to make the cell alive. That itself is irreducible. What would we have to conclude about the simplest and smallest ancestral cell?

Thinking of how small the smallest living cell can be and still retain all the metabolic machinery, the ability to replicate, and to contain enough DNA to support and orchestrate the entire life process ... it all comes down to:

The American biochemist Harold Morowitz speculated what might be the absolute minimum requirement for a completely self replicating cell, deriving essential organic precursors, amino acids, sugars, etc. from its environment but autonomous in every other way in terms of current biochemistry. ...

Such a minimal cell containing, say, three ribosomes, 4 mRNA molecules, a full component of enzymes, a DNA molecule 100,000 nucleotides long and a cell membrane would be about 1000 A (1A = 10-8 cm) in diameter. According to Morowitz:

"This is the smallest hypothetical cell that we can envisage within the context of current biochemical thinking. It is almost certainly a lower limit, since we have allowed no control functions, and no vitamin metabolism and extremely limited intermediary metabolism. Such a cell would be very vulnerable to environmental fluctuation." Denton (ETC) Page 263

Here are two facets of life. First, how simple a proposition is in getting to the first cell at the point of life's origin. Is that simple? Getting the right stuff in the package to start with runs into another probability analysis ... much like the considerations noted in the feature article on chance. Second, the level of complexity of what is inside a putative early cell is at issue. These points are reinforced below by Morowitz and Denton:

The smallest known a bacterial cells, Morowitz continues, have:

"... an average diameter of less than 3000 A. Since the minimum hypothetical cell has a diameter of over 1000 A there is a limited gap in which to seek smaller cells."

The complexity of the smallest known type of cell is so great that it is impossible to accept that such an object would have been thrown together suddenly by some kind of freakish, vastly improbable, event. Such an occurrence would be indistinguishable from a miracle. Denton (ETC) Page 264

Proponents of evolution theory are left in a most precarious place. How can an assumed simple beginning (to cellular life) rely on complexity?

Further, if some of the simplest cellular life forms exhibit 'specified' or 'irreducible complexity,' we are faced with the prospect of an intelligence putting design features in place—again, it is not a matter of gradual appearance or chance. Evolution is not a directed process. If not by chance, how do fully functional cellular components all come together at one time. They come without an antecedent step—no predecessor—that is part way there. At the core, that's the difference between random events and directed (designed) events accounting for life's origin.

Challenges to examples of irreducible complexity have come along. But stepping back to look at the implications for assembling even the constituent parts for the smallest possible cell presents a huge challenge to evolution theory. This is true even for a single functional protein molecule. Further, the composition of an entire cell may not seem as stringent an example compared to a structure that fits the irreducibly complex definition. However, all the constituents noted above—sufficient to make a living cell—still constitutes a complex list of integrated systems. Again, all parts are required within the confines of a cell membrane for life.


You may see there are more potential examples than cited here. Another WindowView page on complex examples provides additional videos to help in considering life is very complex. For now, consider just a couple more points on cell structures and complexity.


Early scientific studies left the impression that the outer envelop of a cell was simply a barrier to the outside world. Over time, the multi-functional nature to the cell membrane emerged. That there is more to a cell membrane is a point is conceded by Monod:

"The development of the metabolic system which as the primordial soup thinned must have " learned " to mobilize chemical potential and to synthesize the cellular components poses Herculean problems. So does the emergence of a selectively permeable membrane without which there can be no viable cell. But the major problem is the origin of the genetic code and of its translational mechanism. Indeed it is not such a problem as a veritable enigma."

There is much more to the cell than the "mere" origin of the protein synthetic apparatus.

Without a cell membrane the components of the protein synthetic apparatus could not be held together. Denton (ETC) Page 268

Science in recent time generates data showing membranes to be selective, with unique molecules for purposes of cell-to-cell recognition, trans-membrane selective transport of molecules, and molecules embedded in the membranes of specific cells hold epigenetic information vital to an organism's early development. Membranes are not simply pass through barriers but also conveyors of information that coordinate at a cell to whole organism level. This multidimensional profiles makes membranes multi-functional. That is simply complexity.

As Denton notes, the apparatus for protein production needs a special environment which the membrane helps to localize as a cell compartment. More than this, inner membrane compartments and specific gel and sol (fluid) zones of the cytoplasm act as regions favoring specific syntheses, like factories with a shop floor marked out by areas with specific activity in the overall production of products. Without the membrane one does not even see the outer building within which the production floor can begin to take form. Take a minute to view a video clip that reveals how cells have compartments with complex structures and unique functions.

[clip from Expelled. Additional videos on complexity
can be viewed HERE.]

Structure of Cilia and Flagella

Two cell structures that are described as machines, with motile action, and are irreducible in complexity are the: Cilium and Flagellum. The complexity of a cilium (singular) and also the flagellum is examined elsewhere in the window.


We revisit this topic here to emphasize structural complexity that functions like a machine yet is a cell structure inside of your body. This is the hair-like apparatus exhibits a sweeping or motile function as described here:

'Motile' (or moving) cilia are found in the lungs, respiratory tract and middle ear. These cilia have a rhythmic waving or beating motion (see right). They work, for instance, to keep the airways clear of mucus and dirt, allowing us to breathe easily and without irritation. They also help propel sperm.

'Non-motile or 'primary' cilia ... They are now recognized as playing crucial roles in a number of organs. Some act as a sensory antenna for the cell, receiving signals from other cells or fluids nearby.

(credit: Ciliopathy Alliance website)

Think of all the particles that float around in the air. You breath air and some particles invariably enter your lungs. But a multitude of little hair-like machines called cilia (plural of cilium) line the passages of your lungs. Like little single bristle brooms, or little paddles, cilia sweep or move the particles up and out of your lungs.

At the core of the cilium is the nature of another micro-miniaturized cellular machine. This is one of the irreducibly complex structures that need all constituent core parts in order for the system to function.

All systems that move by paddling—ranging from my daughter's toy fish to the propeller of a ship—fail if any one of the components is absent. The microtubules are the paddles, whose surface contacts the water and pushes against it. The dynein arms are the motors, supplying the force to move the system. The nexin arms are the connectors, transmitting the force of the motor from one microtubule to its neighbor. Behe (DBB) Page 65

Each part has a vital function. All elements added together make a highly structured and efficient system for motile action. A picture reveals how specialized the structure is:


[more detail on cilia at photo source]

cilia fig 6

The first diagram above is made of several photos from an electron microscope. What you see are images magnified hundreds of thousands of times actual size. The illustration below illustrates the inner structure of the cilia. This is a cross section view. This is hardly a haphazard arrangement of molecules. In fact, specific types of molecular parts allow tor the flex and motile motion of each cilium (see animated example of cilia here).

Bacterial Flagellum

The complexity of a flagellum (singular) with an animated graphic is presented here. Like the cilium, this structure has motile action and propels a bacterium. The specifications of the rotary motor function is remarkable. Some flagella are known to rotate at thousands of revolutions per minute (rpm). The rotary action is driven by

Motor. The bacterial flagellum is driven by a rotary engine (the Mot complex) made up of protein, located at the flagellum's anchor point on the inner cell membrane. The engine is powered by proton motive force, i.e., by the flow of protons (hydrogen ions) across the bacterial cell membrane due to a concentration gradient set up by the cell's metabolism ... The rotor transports protons across the membrane, and is turned in the process. The rotor alone can operate at 6,000 to 17,000 rpm, but with the flagellar filament attached usually only reaches 200 to 1000 rpm. The direction of rotation can be switched almost instantaneously ... .[21] (Source)

In addition to the description above, here are a few of the specifications for the rotary engine:.

· Water-cooled rotary engine, driven by proton motor force.
· Self-assembled and repair.
· Over 250 polypeptides make up over 30 structural parts.
· Each structure must be attached with an exact periodicity along the microtubules.
· In some cases has 2 gears (forward and reverse).
· Operates at speeds usually around 17,000 rpm but seen as high as 100,000 rpm. (Source)

Beyond the engine components described above, some additional 40 proteins are needed for flagellar function.

Again, the idea is we are looking at a complex, multi-molecular machine, that defies explanation by evolution, both as a whole structure but also because each protein within the structure is specified and that relates back to the origin of the genetic information that must also be specific. The shape of each protein is what makes for a specific structural piece of the machine. This scales up an overall complex situation—multiple entities require specific shape and each play a specific role in relation to other parts. All of that has to come together to make the complete and functional machine.


The idea that there is more than one level to a system's complexity can be taken one step further. Not only is a flagellum complex, or a cell membrane multi-functional, or cell proteins highly specified, but we need to step back to think about layers of complexity from a single molecule all the way up to an entire organism. The following block of quoted material from Dr. Wise begins to put this idea in perspective. The first sentence refers to gut bacteria in humans. We are after all an organism which depends on other organisms living within us. And isn't that kind of complex? The gut bacteria ...

These organisms break down molecules we cannot breakdown, providing us with food we would otherwise lack.

... mutual symbiosis exist throughout our world (e.g., cellulose-lignin-digesting microorganisms in the guts of termites; sulfur-reducing bacteria in ocean-vent tubeworms; algae and fungi in lichens; photosynthetic microorganisms in corals).

At a higher level again, communities of organisms are made up of a complex arrangement of a large number of organisms—herbivores and carnivores; pollinators and flowering plants; decomposers; under-story and the upper-story plants, and so on.

Higher than these, the earth and its living organisms exist together in a great network of complex interactions—oxygen used by animals must be produced by photosynthesizers, and carbon dioxide used by plants must be released by animals. The complex interaction of the earth and its life can be seen in how the earth and its life have responded to the changes humankind has made (such as the interaction of fossil-fuel burning in and global climate, the interaction of aerosol sprays and ozone).

On a level even above this, and the earth exists in a complex arrangement of planets, asteroids, moons, stars and galaxies in such a way as to allow life on earth to exist and persist. Wise (CH) Page 229

... the complexity of any one of these levels seems to require an appeal to an intelligent cause. However, the total complexity is at least the sum of the complexities of each level. If the complexity of each level suggests an intelligent cause, the total complexity screams for an intelligent cause. Macroevolutionary theory has never successfully explained the acquisition of any level of this complexity, let alone the total complexity.


Another interesting point here concerns the observed structure of integration. Chemical processes lie within subcellular organelles, subcellular organelles within a cells, cells within tissues. There is a nested hierarchy of complexity in and integration of life on earth. This nested hierarchy of complexity might be expected if it came about by means of the same intelligent cause that brought about the nested hierarchy of classification of biological form. It is not expected by macroevolutionary theory. Wise (CH) Page 230

If this page gets you to thinking on multiple levels with more than one perspective, then you now have added insight. If at any time you hear criticism of a design argument, remember the idea of complexity does not reside in one, two, or more specific structural examples, but overall the systems that support life are layered and as deep as one molecule all the way up th scale to communities at an ecosystem level. To not see complexity from cells to solar system is to be blind sided by the facts taken with narrow focus on only part of the big picture on life.

Quotations from Dr. Michael Denton's "Evolution: A Theory in Crisis" are used by permission of Adler and Adler Publishers Inc., 5530 Wisconsin Ave, Suite 1460, Chevy Chase, MD 20815

Quotations from "The Creation Hypothesis" (CH) edited by J. P. Moreland and "Mere Creation" (MC) edited by William A. Dembski are used by permission of InterVarsity Press, P.O. Box 1400, Downers Grove, IL 60515. All rights reserved. No portion of this material may be used without permission from InterVarsity Press.

Writer / Editor: Dr. T. Peterson, Director,

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Life's Origins Edge of Evolution Billions Missing of Links Case Against Accident >Matter of Days Mystery of Lifes Origin id Evolution Theory Crisis What Darwin Didn't Know Doubts Design Revolution signs
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