reasonable answers

A reader named Andrew has offered a couple of interesting comments on the post “Design Flaws” in the Human Breathing System. I think some worthwhile points have been made in our exchange, so I am copying his comments and my responses to this new entry. This will also allow me to include some of the images and animations cited; plus my second response hit the 4096 character limit for Blogger comments, so it wouldn’t fit in the comment box.

His initial comment:

This article completely misses the point. The problem is not that both tubes have two openings (mouth and nose), but that the esophagus lies above the trachea in the throat, allowing food & liquid to fall into the trachea where they cross. An intelligent design would have the esophagus below the trachea (i.e. at the front of the neck) so gravity would help keep us from choking. You can trace our "wrong" arrangement all the way back to the amphibians and fish from which we evolved. Evolution cannot fix this as it is topologically constrained. But a putative intelligent designer could.

My response:

Thank you for your comment.

Since this article is a response to the claim that the shared opening to the esophagus and trachea is a flawed design and that a "better" design would have independent tubes for breathing and eating, it seems that if anyone has missed the point it is Professor Burdo and the authors of the "If Humans were Built to Last" article.

Second, it is very easy to say that putting the esophagus below the trachea would solve the choking problem, but can you actually demonstrate that this is more than just fanciful speculation? It seems that many of these "design flaw" arguments depend on such hand-waving and speculation as "proof" that a particular design is flawed and that a real intelligent designer would do it this way. See this post on the design of the eye for another common example of this flawed argument.

Third, if you look at diagrams (see below) of the trachea and esophagus, one is not really "above" or "below" the other. When a person is vertical, both tubes are pretty much parallel, and when a person swallows, the more direct route is down the esophagus, while the trachea is the more diverted passageway. It certainly does not seem obvious that gravity would be any help if the two tubes were switched, as you suggested.

Also, there are some good reasons why the esophagus is deeper inside the throat than the trachea. For one, the act of swallowing requires the coordinated workings of a number of muscles; thus switching the location of the esophagus would require a significant reworking of the musculature of our necks, with unpredictable consequences. The point being that again, what seems like such a simple "fix" can have drastic and undesirable consequences, which was the whole point of this article.

Andrew’s 2nd comment:

Hi Ken, thanks for your quick reply.

OK, I admit I didn't read the article you critique, which seems a little silly if it proposes completely separate breathing & eating tubes. As you point out, there are advantages to having multiple openings and also the ability to widen the intake as needed but keep it small most of the time.

Thanks for the diagrams. In both diagrams it seems quite obvious to me that it is risky to have the trachea wide open at the back of the mouth almost all the time. The only thing stopping us from choking to death (or at least coughing like crazy) every time we swallow is the epiglottis flipping down to cover the tracheal opening. That's a neat mechanism, but it has to be extremely reliable. I estimate that we swallow several million times in a lifetime (mostly saliva every minute or so), so a failure rate of just one in a million could lead to premature death by choking. It is an active safety system which needs to work very well because there is no plan B. It would be far more fail-safe to have passive safety designed in, perhaps with an active system on top for extra safety (so that a failure of the active system would not be life-threatening). The only time we are not at risk of something falling down our trachea is when it is covered, but this also stops us from breathing so it must be left open, and at risk, most of the time. It would be much safer to have no connection between the mouth and trachea most of the time, and only connect them on the rare occasions it is needed.

Now, I'm not omniscient so perhaps I'm missing something here, but if I were given this design brief:

1. Get food and liquid into the stomach
2. Get air into the lungs through small openings which can be enlarged if needed on relatively rare occasions
3. Do not under any circumstances let solids or liquids into the lungs

I would:

a. have the esophagus at the front of the neck, directly connected to the back of the mouth without having to leap over the trachea
b. have the trachea behind the esophagus and connected to the back of the sinuses
c. for safety, have no connection between the trachea and mouth under normal circumstances, but have a flap (perhaps like the soft palate) which could open to connect the two as needed for occasional heavy breathing, vocalisation, clearing mucus from the sinuses, etc. - and obviously not when eating or drinking. And have this connection high up at the back of the mouth so that gravity would assist in preventing choking.

True, there may be unforseen problems with this related to musculature etc, but I don't think these would be beyond the problem-solving capacity of a God claimed to be powerful & intelligent enough to create the entire universe from nothing.

-Andrew

My response:

Hi Andrew,

Thank you for your additional commentary on this article. Sorry to keep you waiting. Let me see if I can address some of the things you said:

"The only thing stopping us from choking to death (or at least coughing like crazy) every time we swallow is the epiglottis flipping down to cover the tracheal opening. That's a neat mechanism, but it has to be extremely reliable."

I completely agree with you that the epiglottis is a neat mechanism. I found this wonderful animation (above) showing the process of swallowing. Observe how many steps and parts work together to get food down to the stomach and to protect the respiratory system.  I also agree that the epiglottis must be—and I would add that it indeed is—extremely reliable. Considering how many billions of people are talking and eating at the same time and how there are only a few hundred deaths from choking every year, I would say that the mechanism for protecting people from choking is very reliable from a statistical standpoint.

"It is an active safety system which needs to work very well because there is no plan B. It would be far more fail-safe to have passive safety designed in, perhaps with an active system on top for extra safety (so that a failure of the active system would not be life-threatening)."

Here I would offer some points of disagreement. First, the epiglottis does indeed have passive safety designed in. Note in the animation how in the process of swallowing the epiglottis is levered close by the food being swallowed, such that even if something was preventing the epiglottis from automatically covering the trachea, the epiglottis would still be pushed into position.

Second, there is indeed a "plan B" for the rare instances when the epiglottis does not do its job perfectly. You even mentioned it yourself in your comment. The instant that something other than air begins to pass into the trachea, sensitive nerves trigger the cough reflex to expel the foreign object. This is exactly the kind of redundant active safety system that you seemed to find wanting in the actual design.

"It would be much safer to have no connection between the mouth and trachea most of the time, and only connect them on the rare occasions it is needed."

Safer perhaps in reducing the risk of choking to death (which I must reiterate is already an extremely rare occurrence), but would it necessarily be better? The issue that I have with those who raise the "flawed design" argument is that they tend to focus on just one narrow aspect of the function of a system, and their proposals for "better" designs often ignore many of the other features and functions of the existent design. This is addressed in another article on the supposed design flaws of the vertebrate eye (another common target of the "flawed design" argument). I hope that you can read it and offer your thoughts on it.

"c. for safety, have no connection between the trachea and mouth under normal circumstances, but have a flap (perhaps like the soft palate) which could open to connect the two as needed for occasional heavy breathing, vocalisation, clearing mucus from the sinuses, etc. - and obviously not when eating or drinking. And have this connection high up at the back of the mouth so that gravity would assist in preventing choking."

In this case, I think you greatly underestimate the frequency in which having a connection between the mouth and the trachea is important. As quoted in the article, Richard Deem describes how the mouth and tongue are essential for speech, something that you acknowledge as one of your "as needed" circumstances. But in general humans spend much more time talking and communicating than they do eating and drinking. Thus, under "normal circumstances" it seems logical that the system should be geared for vocalization—with an open connection between mouth and trachea—with a flap (namely, the epiglottis) that is able to close off the connection as needed for eating and drinking.

"True, there may be unforseen problems with this related to musculature etc, but I don't think these would be beyond the problem-solving capacity of a God claimed to be powerful & intelligent enough to create the entire universe from nothing."

This assumes that it is obvious that the current system is not already the most economical and functional design for its purposes, and that your proposed system would indeed be better, but I have to say that you have not convinced me that this is the case.

Diagrams obtained from http://pennstatehershey.org/healthinfo/graphics/images/en/1118.jpg and http://www.tracheostomy.com/resources/surgery/yoursurgery/trachanat2.jpg

“Swallowing” animation from: http://www.linkstudio.info/images/portfolio/medani/Swallow.swf

The following are some excerpts from an insightful and fair-minded essay I read recently by Mike Murray that addresses the “theology bashing” being condoned by various scientists today. He makes one explicit statement that I do not entirely agree with, that “religion is subjective (faith-based),” but I heartily applaud everything else he writes.

“Intelligent Dishonesty (by design)”

by Mike Murray

I have a vague, conceptual belief in some kind of "supreme being." I see that conviction as being not at all at odds with science. I have stated it before and I will repeat it here: There is no belief system -- scientific, religious, or any combination thereof -- that escapes the requirement of faith.

For, to those scientists who say that a god cannot exist since one cannot be proved (and because no one can say from where such a god would have come), the retort is obvious. If the physical matter that presumably exploded in a "Big Bang" wasn't created by a god, from where did that come? If a god did not create the stuff from which the universe supposedly evolved, who -- or what -- did?

If it cannot be proved that "God always was," neither can it be proved that "matter always existed." A degree of faith (or of sticking one's head in the sand) is involved, whichever way you slice it…

-  -  -  -  -  -  -

The presumption of too many people working in scientific positions is thus: science is objective (legitimate), religion is subjective (faith-based). In the matter of the latter, there is no argument; in the case of the former, I disagree.

Scientific methodology calls for observation, experimentation, or contemplation (or some combination of the three) to move a hypothesis to a theory. If other scientists independently replicate a presenter's results -- and if no one succeeds at attempts to disprove the core contention(s) within some period of time -- the proposed theory becomes "accepted" theory. It often remains unproven. Many times, a new theory eventually supplants it.

Hence, even when scientists do make honest efforts at objectivity, actual proof (the hurdle they demand that theologians clear in order to establish legitimacy) is routinely absent in their own work.

The scientists who argue against a Supreme Being's hand in the creation of the universe cite the giants of physics past. They speak of Nicholas Copernicus, who (like Aristarchus in ancient times before him) departed from Ptolemy (Claudius Ptolemaeus), arguing for a solar system in which the Earth circles the Sun -- instead of the other way around. They breathe the name of Galileo Galilei, who suffered house arrest at the hands of the Catholic Church in his later years for defending that very notion.

Those same scientists invoke the memory of Johannes Kepler, who worked out the ellipses that the planets scribe in their journeys around Old Sol. And they recall Isaac Newton's theory of gravity, and then Albert Einstein's revision -- through his work on general relativity -- to bolster their views.

Pretty heady stuff, that. And a most impressive list of experts.

But those making the argument for "matter evolving to consciousness" -- without any help at all from any kind of Creator -- commit a grievous intellectual sin: the sin of omission. For, while they faithfully report some facts relating to the evolution of physics theory, they studiously edit out that which fails to serve their postulates (or, worse, that has the potential of undermining them altogether).

Kepler, Galileo, Newton, Einstein -- they were all seeking to reveal the hand of God, not to disprove it. They were all believers in a Supreme Being, one who they (devoutly) reckoned created the universe. They were all attempting to "read the mind of God," as Einstein (and perhaps Kepler before him) put it. (Stephen Hawking often repeats that phrase -- usually without attribution -- in discussing the Holy Grail of present-day physics: the so-called Unified Theory, the "theory of everything.")…

-  -  -  -  -  -  -

… But I do know one thing. Too many scientists hold theologians to standards to which they, themselves, do not adhere.

For far too many physicists, astronomers, and biologists it's presently a case of "wrong in part, wrong in toto" when it comes to theology. According to them, if there was no actual Garden of Eden (and if there is any chance at all that life exists elsewhere in the universe), then the religious types are all wet.

What if scientists were held to that same standard? They've been wrong many, many times over the centuries. Copernicus (and Aristarchus) proved Ptolemy wrong about his earth-centric system. Kepler corrected the errant notion of circular orbits for planets. Newton likewise altered some earlier-held beliefs while refining his theories about gravitation. Einstein revised Newton and Maxwell. Today, many physicists are hard at work in their efforts to go beyond Einstein, to add to or modify the ideas of Field, Relativity, and Quanta.

In the past, scientists often thought they "knew" things, only to be proved -- at least partially -- wrong by those who followed in their footsteps. If members of society now said to scientists (as many of them are saying to theologians): "Sorry, if you're wrong even a little, you're wrong completely ...and you have nothing to say to us," would they deem it reasonable?

It would be wrong to attack scientists' laudable efforts at observation, experimentation, and contemplation in formulating hypotheses and theories that seek to move our understanding of the physical world forward. It is just as wrong, in my judgment, for scientists to engage in religion-bashing. Regardless of one's personal beliefs on the subject of theology, such activity is uncalled for. Counterproductive, even.

Moreover, a great many of history's giants, working in a variety of scientific fields, have sought to prove God's handiwork -- not to dispel it. To use them today, deceptively (directly or indirectly), in the service of religious detraction is more than heresy. It is intellectual dishonesty.

Copyright ©2006 Michael F. Murray

Earlier this week I visited an opthalmologist for a long overdue eye exam. Among other things, the doctor took an Optomap of my eye—basically a laser image of my retina—to see if there was anything to watch out for back there. She matter-of-factly gave me a 50/50 chance of suffering a retinal detachment in the future… something for me to look forward to.

But this visit, together with some questions on optics and vision asked by my AP Physics students last week, reminded me of just how incredibly intricate our vision is, from the way the placement of our eyeballs gives us stereoscopic vision, to the manner in which our brain interprets and reverses the images so that we see right side up.

An “Inverted” Retina

But in contrast to our intuitive recognition of its wonders, the human eye is often cited as an example of something that is sub-optimally designed, or so flawed that it could not have possibly been designed by an intelligent designer. Now, I know that my own eyes are certainly not optimal—just take a look at how thick my glasses are—but the argument is that even the most perfectly seeing eye is flawed, due to a critical “mistake” in the design of the human eye that can only be explained by an unintelligent evolutionary process rather than an intelligent designer. A sampling of this argument:

But the eye betrays its evolutionary origin with a tell-tale flaw: The retina is inside out. The nerve fibers that carry signals from the retina’s light-sensing cells lie on top of those cells and have to plunge through a large hole in the retina to get to the brain, creating the eye’s blind spot. Any intelligent designer would be offended by such a clumsy arrangement. The human eye was not designed; it was inherited as the result of long-term evolutionary development. (Art Hobson, “Unintelligent Design”)

But only an idiot designer would have the wiring from the image-capture system (i.e. screen sensitive to light) intrude into the darkened cavity through which the light has to pass from lens to image-capture screen. The most blindingly obvious solution, which even a quite severely dumb designer can reasonably be expected to come up with, is to have the image capture aparatus [sic] receive light from one side (the cavity) and have its wiring go out to the image-processing system from its other side. (“Intelligent Design is not a Theory”)

An intelligent designer, working with the components of this wiring, would choose the orientation that produces the highest degree of visual quality. No one, for example, would suggest that the neural connections should be placed in front of the photoreceptor cells -- thus blocking the light from reaching them -- rather than behind the retina. Incredibly, this is exactly how the human retina is constructed. Visual quality is degraded because light scatters as it passes through several layers of cellular wiring before reaching the retina. Granted, this scattering has been minimized because the nerve cells are nearly transparent, but it cannot be eliminated because of the basic design flaw. Moreover, the effects are compounded because a network of vessels, which is needed to supply the nerve cells with a rich supply of blood, also sits directly in front of the light-sensitive layer, another feature that no engineer would propose. (Kenneth Miller, “Life’s Grand Design”)

The above illustration shows the forest of tissues and cells
that light has to travel through to reach the photoreceptor cells.
From http://www.dericbownds.net/bom99/Ch08/Ch08.html

Here is Richard Dawkin’s take:

Any engineer would naturally assume that the photocells would point towards the light, with their wires leading backwards towards the brain. He would laugh at any suggestion that the photocells might point away from the light, with their wires departing on the side nearest the light. Yet this is exactly what happens in all vertebrate retinas. Each photocell is, in effect, wired in backwards, with its wire sticking out on the side nearest the light. The wire has to travel over the surface of the retina, to a point where it dives through a hole in the retina (the so-called ‘blind spot’) to join the optic nerve. This means that the light, instead of being granted an unrestricted passage to the photocells, has to pass through a forest of connecting wires, presumably suffering at least some attenuation and distortion (actually probably not much but, still, it is the principle of the thing that would offend any tidy-minded engineer!). (The Blind Watchmaker, pg. 93)

The squid and the octopus are seen as examples of the way that an eye should be designed, or the “Obviously Correct Solution” as the writer of one of the above quotes put it. The image at the right compares the cephalopods verted retina with the inverted human retina (from “The Evolution of the Human Eye” by Sean D. Pitman).

A Designer Faux Pas?

So what’s up with this? Did Someone make a mistake in the design of the human eye? Or is this really an example of a perfectly natural evolutionary error? The answer is: Neither! To call the inverted retina a “design flaw” or an “error” is to turn a blind eye to the intricately coordinated series of systems and structures designed to bring clarity of vision to humans.

When an example of “sub-optimal” design is singled out, critics often focus narrowly on one apparently compromised aspect of a system, and miss seeing the big picture of how the entire system works as a cohesive and finely tuned whole. See my previous post on “Design Flaws” in the Human Breathing System” for another example. Though at first the inverted retina appears to be a backward design, a deeper understanding of the eye reveals just how purposefully the parts were arranged, such that optical engineers today are gaining new ideas on how to dramatically improve sensing equipment by applying the techniques used in the eye.

The Greedy Photoreceptors

Those who have studied the vertebrate eye in depth have concluded that, rather than being a “flawed design,” the inverted retina appears to be an ideal and necessary solution to the specific demands of the eye’s photoreceptors.

Biochemist Michael Denton writes, “[C]onsideration of the very high energy demands of the photoreceptor cells in the vertebrate retina suggests that rather than being a challenge to teleology the curious inverted design of the vertebrate retina may in fact represent a unique solution to the problem of providing the highly active photoreceptor cells of higher vertebrates with copious quantities of oxygen and nutrients” (“The Inverted Retina: Maladaptation or Pre-adaptation?” Origins and Design 19:2). He describes the incredible capability of the mammalian photoreceptor to detect even a single photon of light. This extreme sensitivity comes at a price, a “greedy” need for both nutrients and oxygen. These are provided for by a layer of capillaries (seen at the bottom of the illustration at left) connected to the photoreceptors by the retinal pigment epithelium (RPE). Without this continuous maintenance, our photoreceptor cells would quickly overload and stop functioning. This layer of capillaries and the RPE would completely block light from the photoreceptors if they were facing the inner surface of the retina, hence the need for the “inverted” retina.

Westmont College biology professor George Ayoub, goes in-depth on the importance of the RPE in his article, “On the Design of the Vertebrate Retina,” Origins and Design 17:1. From the abstract:

It has been commonly claimed that the vertebrate eye is functionally suboptimal, because photoreceptors in the retina are oriented away from incoming light. However, there are excellent functional reasons for vertebrate photoreceptors to be oriented as they are. Photoreceptor structure and function is maintained by a critical tissue, the retinal pigment epithelium (RPE), which recycles photopigments, removes spent outer segments of the photoreceptors, provides an opaque layer to absorb excess light, and performs additional functions. These aspects of the structure and function of the vertebrate eye have been ignored in evolutionary arguments about suboptimality, yet they are essential for understanding how the eye works.

He also addresses the issue of the “blind spot” and engages in a thought experiment that shows that visual acuity would actually degrade significantly if the human eye was wired any other way. So rather than being “wired wrong,” it seems that this is exactly the most optimal solution for our vision.

Living Optical Fibers

So is the degradation in image quality as light passes through these nerves and blood vessels an adverse but necessary compromise for our eyes? I would suggest that the more appropriate question here is, “Who says that image quality in our eye is compromised?” The statements given by evolutionists like Dawkins, Miller, and others imply that the inverted retina is obviously sub-optimal, and that visual quality is of course degraded by the fact that light has to travel through all those layers of cells and tissue. But is any evidence provided that image quality is actually compromised? The truth is that vertebrates generally have the sharpest visual acuity of all animal species, but how is this possible given such a backwards arrangement of the vertebrate retina?

A fantastic study conducted in 2007 explored this very question, and what they discovered was a new function of a certain type of cell in the vertebrate eye that in essence serves as biological “fiber optics” to channel light through the retinal layers to the photoreceptors. The study was titled “Müller cells are living optical fibers in the vertebrate retina” (2007) and was published in the Proceedings of the National Academy of Sciences (PNAS)104 (20): 8287-8292. The below graphic from the study illustrates how these Müller glial cells collect light from the inner surface of the retina and transmit it virtually intact through the layers of nerves and tissue to the photoreceptors.

From the abstract:

“…these cells provide a low-scattering passage for light from the retinal surface to the photoreceptor cells. Using a modified dual-beam laser trap we could also demonstrate that individual Müller cells act as optical fibers. Furthermore, their parallel array in the retina is reminiscent of fiberoptic plates used for low-distortion image transfer. Thus, Müller cells seem to mediate the image transfer through the vertebrate retina with minimal distortion and low loss.”

An interesting summary of the study and their technique can be found here, and includes the below graphic comparing an artificial fiber optic panel with Müller cells, the “living optical fibers.”

Comparison of Müller cells with a fiber-optic plate (FOP). Bottom row shows an image (left) transmitted through a FOP (center) and through a retina (right).
From http://www.vision-research.eu/index.php?id=160

Some additional fascinating details emerge from this article. Müller cells span the entire thickness of the retina, and widen at the inner surface into funnels that cover the entire retinal surface, thus making it possible, according to the researchers, to capture every photon that enters the eye. As the researchers described, “[T]he funnel-shape of Müller cells and their refractive index gradient provide an optimal optical coupling of the retina to the vitreous. Thus, Müller cells not only allow low-loss light transfer through the scattering inner retinal layers to the photoreceptor cells but also optimize the coupling of the retina to the transparent media of the eye.” No talk of sub-optimality here—quite the reverse, in fact.

Lead researcher Andreas Reichenbach commented, “Nature is so clever. This means there is enough room in the eye for all the neurons and synapses and so on, but still the Müller cells can capture and transmit as much light as possible” (quoted in “Living optical fibres found in the eye” by Lucy Sherriff). The design of these cells is so efficient that it could very well provide the innovation for the next generation of fiber optic technology. The ability of these Müller cells to transmit light from a wide surface area through such a small tube can lead to new “intelligent” sensors that incorporate computer circuitry attached to more compact fiber optic bundles.

To say that a design is “sub-optimal” is to imply that there is a better way to do something. So the next time you hear someone comment about the “flawed design” of the human eye, ask them to elaborate on what aspect of the eye they consider to be flawed. Is there any better way to wire the photoreceptor cells that would still connect them with the replenishing blood flow necessary to maintain sustained vision? And what reason is there to talk of “degraded visual quality” when the eye features living optical fibers that transmit images with greater efficiency than the best optical plate that engineers have devised?

The “flaw,” it seems, is not in the actual design of the eye itself, but rather in that person’s understanding of the degree of integration and coordination exhibited by all the parts making up the purposeful and optimal design of the eye.

Additional Resources and References

“Living Fibre Optics Light Up Our Eyes” – An excellent illustrated description of the 2007 study on Müller cells, with great pictures! Also describes how engineers hope to adapt the design of these cells into fiber optic technology.

Andreas Reichenbach, et al., “Müller cells are living optical fibers in the vertebrate retina”

George Ayoub, “On the Design of the Vertebrate Retina,” Origins and Design 17:1

Jerry Bergman, “Inverted Human Eye a Poor Design?,” Perspectives on Science and Christian Faith 52 (March 2000): 18-30

Michael Denton, “The Inverted Retina: Maladaptation or Pre-adaptation?” Origins and Design 19:2

Rich Deem, “Bad Designs in Biology? Why the "Best" Examples Are Bad” – A discussion of the common examples of “bad design” in biology are not so bad after all.

Sean D. Pitman, “The Evolution of the Human Eye”

Image Credits

Optomap retina image courtesy of Optos.com

All other images linked to their original sources.

One of my wittier students put this as her answer (in lieu of an actual solution) to a problem on a recent Physics test on Newton’s Laws:

"Help me, Mr. Yeh-Kenobi! You are my only hope!”

My immediate response,

“Use the Force (=mass times acceleration), Beth!”

Her table got a kick out of that when I handed back the test.