January 1st, 2008
A sad way to start the new year: Skippy got run over by a car. I was out in the front, working on the van. Skippy, our long-haired Chihuahua, who also answers to “Rat” or “The Wimp” or anything else as long as it’s spoken in a cheerful tone, was let out of the house to answer nature’s call. He cantered gaily down to the corner, and I customarily ignored his actions and whereabouts. But suddenly the cold air was cut by the sound of tires screeching, followed by a thunk, and a YIPE. I jerked my head in the direction of the commotion just in time to see a small cloud of familiarly-hued blond hair blow past. A white sedan with an elderly couple sheepishly pulled over, and then our dumb little Chihuahua, shocked and bleeding, stumbled onto the neighbor’s front lawn.
I never had the intention of owning a Chihuahua, but my dear wife Lori thought she’d do something special for our 12 year old daughter Summerlyn. I’m sure my media savvy daughter wasn’t influenced by Paris Hilton’s Tinkerbell, or Britney Spear’s BitBit, or even Hilary Duff’s Chiquita. No, I’m confident she was inspired to own such a fine example of artificial selection all by herself. Thus, after searching on craigslist last Spring, the girls found a cute Chihuahua puppy to the tune of four hundred of my dollars.
Anyway, the Wimp was hurt but very much alive. Apparently he was just banged up by the underside of the car, not literally run over. I whipped out my cell phone to call Lori, the old man expressed his apologies, and I cringed at the lack of responsibility we exercised by letting him roam unsupervised. The girls wrapped him up and spirited him to the vet’s and the white sedan slowly departed. I went back to work on the van, upset by the incident but determined to spend this last day of my Christmas vacation accomplishing at least one major “honey-doo.”
The starter of Lori’s Nissan Quest had died the day before, and I was trying to replace it myself. Not being a mechanic by any stretch of the imagination, I first looked through the owner’s manual for guidance. Not finding anything, I browsed the internet and found manufacturer’s toggle diagrams of starters, but nothing about where they were located. Finally I just opened the hood, peered around dirty black tubing, and figured it out the old-fashioned hands-on sort of way. I summoned up my “can do” spirit, remembered the cautionary advice from the auto parts guy about disconnecting the positive battery cable (or was it the negative cable?), and began removing the retired component in a man versus machine tussle of torque and elbow grease.
I thought of poor, injured Skippy and wondered what sort of damages he endured. I later learned that he had vomited blood at the vet’s. Were internal organs ruptured? While I labored at the starter, my mind wandered. Studying the automotive entrails under the hood made me think in anatomical terms. All those parts seem like organs, like organ systems, throbbing mechanical devices linked by rubber-coated copper neurons and gas-conducting arterioles. I began to draw parallels between Skippy’s, and my own, anatomy and that of the machine. How like us the automobile seems to be: it requires a source of fuel, storing it in a 20 gallon metal stomach, and pumping it rhythmically to the engine in a manner reminiscent of peristalsis. The ignition stimulates the engine like the activation energy of a chemical reaction, like digestion, and the engine itself mimics the high metabolic rate of a hot-blooded animal. Impulses circulate through the electrical system like the firing of so many sensory and (ahem) motor neurons. Fluids are pumped, joints are lubricated in grease like the synovial fluid bathing our joints, and carbon-based gaseous wastes exit the system through a network of piping, just like you-know-what.
This comparison reminded me of the argument for the existence of God expressed in Natural Theology, the most seminal work produced by the early nineteenth century philosopher William Paley. Using a watch as his now iconic example, he expressed how so elegantly contrived a device would have had to have been conceived and fabricated by someone, and for a purpose. Elevating this argument to a grander scale, he argued that the beauty of nature and all its wondrous inhabitants must have similarly been conceived and fabricated by the hands of God. Watch: Man as Nature: God. The complicated structures in my van were obviously designed and assembled by engineers and laborers (or robots) respectively. The lungs and heart, the branching network of vessels comprising the circulatory system, and the enzyme-powered digestive tract are even more complicated, and so it stands to reason that these must also have been designed and assembled by some creative and intelligent Someone.
In the pre-Darwin milieu this deduction made perfect sense. Intricate machines like pocket watches must have had artificers, and a reasonable extrapolation was that vastly more intricate biological organs, like the human brain or eye, must also have had an artificer—one vastly more creative and capable.
But then that pesky Victorian-age evolutionist came along and politely but forcefully ruined the whole neatly packaged explanation. One way he did this was by pointing out certain curiosities in the bodies of living organisms: the vestigial structures. These, he argued, were aspects of our anatomy that didn’t quite make sense unless viewed from the position that organisms have a history, and were not created in their present day forms. These structures, rudimentary and sometimes useless, are perplexing if we don’t accept that they were inherited from ancestors that used them more prominently. Why would the flightless kiwi sport miniscule wings unless it descended from birds with actual flying limbs; why would the blind mole rat have its sightless eyes, puny and covered with a layer of skin, unless it descended from sighted ancestors?
One of my favorites (yes, eccentric biology teachers can have favorite vestigial structures) is the snake’s left lung. In fact, I’m selecting this bizarre little organ for the title of this new blog. Seeing this structure, this underdeveloped little nub, is, for the curious, an eye-opening encounter. It is less than one tenth the size of the right lung, and one has to wonder about its existence. It is diminutive and non-functioning, so why is it even there in the first place? The evolutionary answer is simple: the Cretaceous ancestors of snakes (burrowing varanid lizards or marine mosasaurs; there are two hypotheses), had the typical paired lungs of any lizard. But as early snakes developed into their characteristic serpentine form, the need for a long narrow body necessitated internal organ modification: apparently a single elongate lung more effectively uses the limited space than a pair of standard lizard lungs. Over time, natural selection favored the development of an asymmetrical respiratory system, but it left behind a tiny reminder of the standard paired lung condition.
Since William Paley had died years before Darwin’s insight transformed the science of biology, it’s impossible to know how he would have personally dealt with it. What would he have to say about the snake’s left lung? Modern creationists are not shy about sharing their opinions regarding vestigial structures (although I have yet to find any cogent discussion of the snake lung question.) The standard creationist approach begins with the allegation that scientists claim all vestigial structures to be totally useless. This is followed, usually in checklist fashion, with descriptions of the important functions that all these organs and parts have, thus nullifying the scientist’s claim. Usually the vestigial structures described are limited to those of the human body (the appendix and the coccyx being the most commonly used examples) and the discussion is often summarized with a reassuring comment about God making the entire body and therefore having uses for every last part.
There is a major problem with this argument: nothing in biology requires that a structure has to be functionless to be considered vestigial. The structure may be rudimentary, but it may also have some, if minor, role to play. Darwin described it as a matter of no longer serving its “proper purpose.” For example, the vermiform appendix is, in mammals that have a well developed one, a cellulose-fermenting caecum. In humans it plays a role in the development of the immune system plus it secretes some lubricating mucus which aids in movement. Similarly the coccyx, the tiny remnant of a tail bone at the base of our pelvis, does attach some muscles, but it is obviously not an external tail used for balance or grasping as it is in other mammals. Both of these structures, while both performing some beneficial function (though not quite as vital as the creationist literature makes it out to be) are no longer playing the proper role they would in a more developed state.
So vestigial structures can possibly have a function, and there exists a continuum, from those that retain their original function but are not quite developed, to those that no longer serve the proper purpose but have taken on alternative roles, to those that truly are rudimentary to the point of being useless. But, again, it is not required for the structure to be absolutely useless to be vestigial, in fact even the term “vestigial” comes from the Latin word “vestigium”, which is a footprint or trace, and in the case of biology an indication about the physiology or ecology of the ancestors, but not by definition necessarily useless.
As a result, this creationist argument ends up being a straw man argument: setting evolutionary biologists up as uninformed scientists claiming vestigial structures to be completely useless, and then knocking them down with vivid descriptions of the uses. The fact that little of the creationist literature abides by the true meaning of vestigiality is telling: they are either truly unaware of it, or they are trying to redefine scientific terms to maintain their anti-evolution arsenal.
Vestigial structures are fascinating and inform us about the lineages from which organisms descended. We can surmise that blind cave fish had ancestors with actual eyes based on the fact that they now have (eyeless) eye sockets. We can infer that dandelions, which are now self-pollinating flowers, descended from ancestors which actually needed those showy yellow petals to attract pollinators. Sometimes they’re intimately close to home such as the goose-bumps you experience when you’re cold or frightened. These occur when the tiny erector pili muscles contract and cause your sparse body hair to stand up. In furrier mammals this action traps a nice film of warm air against the skin, and it could be argued that in hairier members of our population this trait is somewhat effective. But the vestigial reflex for this action to occur when we are frightened is obviously no longer something to count on. House cats may intimidate rivals by puffing up their fur, but do you really look more imposing when some chilling event raises the hair on your back?
Curiously there is another, less frequently used, creationist argument; usually only used when it appears that the organ in question truly is reduced to the point of being functionless, like the eye sockets in blind cave fish. In these cases it is claimed that the vestigial structure is a sign of decay, of degeneration because we live in a “fallen world.” This claim that is dependent on treating the story of Adam’s Fall as a factual event with consequences that shaped the physical universe. It’s a theological position relying more on Biblical loyalty than on scientific references (although some creationists, like the late A.E. Wilder-Smith, conflate the degradation after the Biblical Fall with the physical law of entropy, and try to apply it to biology with speculations about a loss of genetic information.) What is interesting is that, when you think about it, these two arguments aren’t exactly compatible. How can vestigial body parts, which in creationist reality are all functional structures essential to the body, also be the result of a degraded loss of genetic information due to the Fall of man?
Anyway, back to the van. Is it the product of evolution? Well, yes and no. It’s more complicated than its predecessors. Everything from the engine to the glass of the windshield has transformed over the years, even the electrical horn produces far more decibels than the hand-squeezed honkers of yesteryear. And since these parts are largely refinements of preexisting structures, the automobile does indeed show, in Darwin’s parlance, descent with modification. Additionally there exists of fossil record of sorts in the form of car manufacturer catalogs, or Consumer Reports magazines, or Kelly Blue Books. If one were to stack these publications in chronological order, then digging down to the progressively older copies would be like uncovering fossiliferous strata. But, on the other hand, the cars are obviously assembled in factories by industrious workers and automations, and not literally reproducing and passing down favorable traits in the way biological entities demonstrate natural selection. Thus, this illustration is a bit of a hybrid, if anything analogizing theistic evolution.
Well, time to put away the scientific debates and theological conundrums, and return to the important things in life—like my daughter’s wimpy little dog and my broken van. The vet called later that night. Skippy is spending the night there but he ended up all right. He lost a pair of claws, his paw swelled up tremendously (but temporarily), he had patches of missing fur, and was generally banged up. But there were no broken bones or ruptured organs; his sanguivorine vomit came from licking his wounds and ingesting so much blood. He’ll live to pester us as before. The visit costs me $900., for morphine, and an I.V. Skippy’s net value has suddenly tripled. On the other hand, I managed to successfully change the starter, and that saved me $80. or more in labor costs. I just hope there won’t be any more repairs to make for a long time, to the van, to Skippy, or even to myself—such as a ruptured appendix or a broken tail bone.
A sad way to start the new year: Skippy got run over by a car. I was out in the front, working on the van. Skippy, our long-haired Chihuahua, who also answers to “Rat” or “The Wimp” or anything else as long as it’s spoken in a cheerful tone, was let out of the house to answer nature’s call. He cantered gaily down to the corner, and I customarily ignored his actions and whereabouts. But suddenly the cold air was cut by the sound of tires screeching, followed by a thunk, and a YIPE. I jerked my head in the direction of the commotion just in time to see a small cloud of familiarly-hued blond hair blow past. A white sedan with an elderly couple sheepishly pulled over, and then our dumb little Chihuahua, shocked and bleeding, stumbled onto the neighbor’s front lawn.
I never had the intention of owning a Chihuahua, but my dear wife Lori thought she’d do something special for our 12 year old daughter Summerlyn. I’m sure my media savvy daughter wasn’t influenced by Paris Hilton’s Tinkerbell, or Britney Spear’s BitBit, or even Hilary Duff’s Chiquita. No, I’m confident she was inspired to own such a fine example of artificial selection all by herself. Thus, after searching on craigslist last Spring, the girls found a cute Chihuahua puppy to the tune of four hundred of my dollars.
Anyway, the Wimp was hurt but very much alive. Apparently he was just banged up by the underside of the car, not literally run over. I whipped out my cell phone to call Lori, the old man expressed his apologies, and I cringed at the lack of responsibility we exercised by letting him roam unsupervised. The girls wrapped him up and spirited him to the vet’s and the white sedan slowly departed. I went back to work on the van, upset by the incident but determined to spend this last day of my Christmas vacation accomplishing at least one major “honey-doo.”
The starter of Lori’s Nissan Quest had died the day before, and I was trying to replace it myself. Not being a mechanic by any stretch of the imagination, I first looked through the owner’s manual for guidance. Not finding anything, I browsed the internet and found manufacturer’s toggle diagrams of starters, but nothing about where they were located. Finally I just opened the hood, peered around dirty black tubing, and figured it out the old-fashioned hands-on sort of way. I summoned up my “can do” spirit, remembered the cautionary advice from the auto parts guy about disconnecting the positive battery cable (or was it the negative cable?), and began removing the retired component in a man versus machine tussle of torque and elbow grease.
I thought of poor, injured Skippy and wondered what sort of damages he endured. I later learned that he had vomited blood at the vet’s. Were internal organs ruptured? While I labored at the starter, my mind wandered. Studying the automotive entrails under the hood made me think in anatomical terms. All those parts seem like organs, like organ systems, throbbing mechanical devices linked by rubber-coated copper neurons and gas-conducting arterioles. I began to draw parallels between Skippy’s, and my own, anatomy and that of the machine. How like us the automobile seems to be: it requires a source of fuel, storing it in a 20 gallon metal stomach, and pumping it rhythmically to the engine in a manner reminiscent of peristalsis. The ignition stimulates the engine like the activation energy of a chemical reaction, like digestion, and the engine itself mimics the high metabolic rate of a hot-blooded animal. Impulses circulate through the electrical system like the firing of so many sensory and (ahem) motor neurons. Fluids are pumped, joints are lubricated in grease like the synovial fluid bathing our joints, and carbon-based gaseous wastes exit the system through a network of piping, just like you-know-what.
This comparison reminded me of the argument for the existence of God expressed in Natural Theology, the most seminal work produced by the early nineteenth century philosopher William Paley. Using a watch as his now iconic example, he expressed how so elegantly contrived a device would have had to have been conceived and fabricated by someone, and for a purpose. Elevating this argument to a grander scale, he argued that the beauty of nature and all its wondrous inhabitants must have similarly been conceived and fabricated by the hands of God. Watch: Man as Nature: God. The complicated structures in my van were obviously designed and assembled by engineers and laborers (or robots) respectively. The lungs and heart, the branching network of vessels comprising the circulatory system, and the enzyme-powered digestive tract are even more complicated, and so it stands to reason that these must also have been designed and assembled by some creative and intelligent Someone.
In the pre-Darwin milieu this deduction made perfect sense. Intricate machines like pocket watches must have had artificers, and a reasonable extrapolation was that vastly more intricate biological organs, like the human brain or eye, must also have had an artificer—one vastly more creative and capable.
But then that pesky Victorian-age evolutionist came along and politely but forcefully ruined the whole neatly packaged explanation. One way he did this was by pointing out certain curiosities in the bodies of living organisms: the vestigial structures. These, he argued, were aspects of our anatomy that didn’t quite make sense unless viewed from the position that organisms have a history, and were not created in their present day forms. These structures, rudimentary and sometimes useless, are perplexing if we don’t accept that they were inherited from ancestors that used them more prominently. Why would the flightless kiwi sport miniscule wings unless it descended from birds with actual flying limbs; why would the blind mole rat have its sightless eyes, puny and covered with a layer of skin, unless it descended from sighted ancestors?
One of my favorites (yes, eccentric biology teachers can have favorite vestigial structures) is the snake’s left lung. In fact, I’m selecting this bizarre little organ for the title of this new blog. Seeing this structure, this underdeveloped little nub, is, for the curious, an eye-opening encounter. It is less than one tenth the size of the right lung, and one has to wonder about its existence. It is diminutive and non-functioning, so why is it even there in the first place? The evolutionary answer is simple: the Cretaceous ancestors of snakes (burrowing varanid lizards or marine mosasaurs; there are two hypotheses), had the typical paired lungs of any lizard. But as early snakes developed into their characteristic serpentine form, the need for a long narrow body necessitated internal organ modification: apparently a single elongate lung more effectively uses the limited space than a pair of standard lizard lungs. Over time, natural selection favored the development of an asymmetrical respiratory system, but it left behind a tiny reminder of the standard paired lung condition.
Since William Paley had died years before Darwin’s insight transformed the science of biology, it’s impossible to know how he would have personally dealt with it. What would he have to say about the snake’s left lung? Modern creationists are not shy about sharing their opinions regarding vestigial structures (although I have yet to find any cogent discussion of the snake lung question.) The standard creationist approach begins with the allegation that scientists claim all vestigial structures to be totally useless. This is followed, usually in checklist fashion, with descriptions of the important functions that all these organs and parts have, thus nullifying the scientist’s claim. Usually the vestigial structures described are limited to those of the human body (the appendix and the coccyx being the most commonly used examples) and the discussion is often summarized with a reassuring comment about God making the entire body and therefore having uses for every last part.
There is a major problem with this argument: nothing in biology requires that a structure has to be functionless to be considered vestigial. The structure may be rudimentary, but it may also have some, if minor, role to play. Darwin described it as a matter of no longer serving its “proper purpose.” For example, the vermiform appendix is, in mammals that have a well developed one, a cellulose-fermenting caecum. In humans it plays a role in the development of the immune system plus it secretes some lubricating mucus which aids in movement. Similarly the coccyx, the tiny remnant of a tail bone at the base of our pelvis, does attach some muscles, but it is obviously not an external tail used for balance or grasping as it is in other mammals. Both of these structures, while both performing some beneficial function (though not quite as vital as the creationist literature makes it out to be) are no longer playing the proper role they would in a more developed state.
So vestigial structures can possibly have a function, and there exists a continuum, from those that retain their original function but are not quite developed, to those that no longer serve the proper purpose but have taken on alternative roles, to those that truly are rudimentary to the point of being useless. But, again, it is not required for the structure to be absolutely useless to be vestigial, in fact even the term “vestigial” comes from the Latin word “vestigium”, which is a footprint or trace, and in the case of biology an indication about the physiology or ecology of the ancestors, but not by definition necessarily useless.
As a result, this creationist argument ends up being a straw man argument: setting evolutionary biologists up as uninformed scientists claiming vestigial structures to be completely useless, and then knocking them down with vivid descriptions of the uses. The fact that little of the creationist literature abides by the true meaning of vestigiality is telling: they are either truly unaware of it, or they are trying to redefine scientific terms to maintain their anti-evolution arsenal.
Vestigial structures are fascinating and inform us about the lineages from which organisms descended. We can surmise that blind cave fish had ancestors with actual eyes based on the fact that they now have (eyeless) eye sockets. We can infer that dandelions, which are now self-pollinating flowers, descended from ancestors which actually needed those showy yellow petals to attract pollinators. Sometimes they’re intimately close to home such as the goose-bumps you experience when you’re cold or frightened. These occur when the tiny erector pili muscles contract and cause your sparse body hair to stand up. In furrier mammals this action traps a nice film of warm air against the skin, and it could be argued that in hairier members of our population this trait is somewhat effective. But the vestigial reflex for this action to occur when we are frightened is obviously no longer something to count on. House cats may intimidate rivals by puffing up their fur, but do you really look more imposing when some chilling event raises the hair on your back?
Curiously there is another, less frequently used, creationist argument; usually only used when it appears that the organ in question truly is reduced to the point of being functionless, like the eye sockets in blind cave fish. In these cases it is claimed that the vestigial structure is a sign of decay, of degeneration because we live in a “fallen world.” This claim that is dependent on treating the story of Adam’s Fall as a factual event with consequences that shaped the physical universe. It’s a theological position relying more on Biblical loyalty than on scientific references (although some creationists, like the late A.E. Wilder-Smith, conflate the degradation after the Biblical Fall with the physical law of entropy, and try to apply it to biology with speculations about a loss of genetic information.) What is interesting is that, when you think about it, these two arguments aren’t exactly compatible. How can vestigial body parts, which in creationist reality are all functional structures essential to the body, also be the result of a degraded loss of genetic information due to the Fall of man?
Anyway, back to the van. Is it the product of evolution? Well, yes and no. It’s more complicated than its predecessors. Everything from the engine to the glass of the windshield has transformed over the years, even the electrical horn produces far more decibels than the hand-squeezed honkers of yesteryear. And since these parts are largely refinements of preexisting structures, the automobile does indeed show, in Darwin’s parlance, descent with modification. Additionally there exists of fossil record of sorts in the form of car manufacturer catalogs, or Consumer Reports magazines, or Kelly Blue Books. If one were to stack these publications in chronological order, then digging down to the progressively older copies would be like uncovering fossiliferous strata. But, on the other hand, the cars are obviously assembled in factories by industrious workers and automations, and not literally reproducing and passing down favorable traits in the way biological entities demonstrate natural selection. Thus, this illustration is a bit of a hybrid, if anything analogizing theistic evolution.
Well, time to put away the scientific debates and theological conundrums, and return to the important things in life—like my daughter’s wimpy little dog and my broken van. The vet called later that night. Skippy is spending the night there but he ended up all right. He lost a pair of claws, his paw swelled up tremendously (but temporarily), he had patches of missing fur, and was generally banged up. But there were no broken bones or ruptured organs; his sanguivorine vomit came from licking his wounds and ingesting so much blood. He’ll live to pester us as before. The visit costs me $900., for morphine, and an I.V. Skippy’s net value has suddenly tripled. On the other hand, I managed to successfully change the starter, and that saved me $80. or more in labor costs. I just hope there won’t be any more repairs to make for a long time, to the van, to Skippy, or even to myself—such as a ruptured appendix or a broken tail bone.
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