You've misunderstood your classes. Vestigial organs do not cease to be vestigial if they have a function. They are vestigial if they no longer serve their *original* function.
Above is from http://www.talkorigins.org/indexcc/CB/CB360.html.Claim CB360:
Practically all "vestigial" organs in man have been shown to have definite uses and not to be vestigial at all.Source:
Morris, Henry M., 1974. Scientific Creationism, Green Forest, AR: Master Books, pp. 75-76.Response:
- "Vestigial" does not mean an organ is useless. A vestige is a "trace or visible sign left by something lost or vanished." Examples from biology include leg bones in snakes, eye remnants in blind cave fish [Yamamoto and Jeffery 2000], extra toe bones in horses, wing stubs on flightless birds and insects, and molars in vampire bats. Whether these organs have functions or not is irrelevant. They obviously do not have the function that we expect from such parts in other animals, which creationists say the parts are "designed" for.
Vestigial organs are evidence for evolution because we expect evolutionary changes to be imperfect as creatures evolve to adopt new niches. Creationism cannot explain vestigial organs. They are evidence against creationism if the creator follows a basic design principle that form follows function, as Morris himself expects [1974, p. 70]. They are compatible with creation only if anything and everything is compatible with creation, making creationism useless and unscientific.
- Some vestigial organs can be determined to be useless if experiments show that organisms with them survive no better than organisms without them.
Links:
Theobald, Douglas, 2004. 29+ Evidences for macroevolution: Prediction 2.1: Anatomical vestiges. http://www.talkorigins.org/faqs/comdesc/section2.html#morphological_vestigesReferences:
- Morris, H., 1974. (see above).
- Yamamoto, Y. and W. R. Jeffery., 2000. Central role for the lens in cave fish eye degeneration. Science 289(5479): 631-633.
Above is from http://www.talkorigins.org/faqs/comdesc/section2.htmlPrediction 2.1: Anatomical vestiges
"The wing of the ostrich resembles those of the gyrfalcon and the hawk. Who does not know how the speed of the gyrfalcon and hawk in flight exceeds that of other birds? The ostrich certainly has wings like theirs but not their speed of flight. Truly, it has not the capacity to be lifted from the ground and gives only the impression of spreading its wings as if to fly; however, it never supports itself above the earth in flight.
It is exactly the same with all those hypocrites who pretend to live a life of piety, giving the impression of holiness without the reality of holy behaviour."
The Aberdeen Bestiary
Folio 41v , c. AD 1200
— on the ostrich, its vestiges a symbol of hypocricy since the 2nd century A.D.Some of the most renowned evidence for evolution are the various nonfunctional or rudimentary vestigial characters, both anatomical and molecular, that are found throughout biology. A vestige is defined, independently of evolutionary theory, as a reduced and rudimentary structure compared to the same complex structure in other organisms. Vestigial characters, if functional, perform relatively simple, minor, or inessential functions using structures that were clearly designed for other complex purposes. Though many vestigial organs have no function, complete non-functionality is not a requirement for vestigiality (Crapo 1985; Culver et al. 1995; Darwin 1872, pp. 601-609; Dodson 1960, p. 44; Griffiths 1992; McCabe 1912, p. 264; Merrell 1962, p. 101; Moody 1962, p. 40; Muller 2002; Naylor 1982; Strickberger 2000; Weismann 1886, pp. 9-10; Wiedersheim 1893, p. 2, p. 200, p. 205).
For example, wings are very complex anatomical structures specifically adapted for powered flight, yet ostriches have flightless wings. The vestigial wings of ostriches may be used for relatively simple functions, such as balance during running and courtship displays—a situation akin to hammering tacks with a computer keyboard. The specific complexity of the ostrich wing indicates a function which it does not perform, and it performs functions incommensurate with its complexity. Ostrich wings are not vestigial because they are useless structures per se, nor are they vestigial simply because they have different functions compared to wings in other birds. Rather, what defines ostrich wings as vestigial is that they are rudimentary wings which are useless as wings.
Vestigial structures have perplexed naturalists throughout history and were noted long before Darwin first proposed universal common descent. Many eighteenth and nineteenth century naturalists identified and discussed vestigial structures, including Johann Wolfgang von Goethe (1749-1832), Georges-Louis Leclerc, Compte de Buffon (1707-1788), and Georges Cuvier (1769-1832). Over sixty years before Darwin's publication of On the Origin of Species, the eminent French anatomist Geoffroy St. Hilaire (1772-1844) discussed his observations of the vestigial wings of the cassowary and ostrich during his travels with Napoleon to Egypt:
"There is another species that, like the ostrich, never leaves the ground, the Cassowary, in which the shortening [of the wing] is so considerable, that it appears little more than a vestige of a wing. Its arm is not, however, entirely eliminated. All of the parts are found under the skin. ...
Whereas useless in this circumstance, these rudiments of the furcula have not been eliminated, because Nature never works by rapid jumps, and She always leaves vestiges of an organ, even though it is completely superfluous, if that organ plays an important role in the other species of the same family. Thus, under the skin of the Cassowary's flanks are the vestiges of the wings ..." (Geoffroy 1798)
Geoffroy was at a loss for why exactly nature "always leaves vestiges of an organ", yet he could not deny his empirical observations. Ten years later, Jean-Baptiste Lamarck (1744-1829) identified several vestigial structures in his Zoological Philosophy (Lamarck 1809, pp. 115-116):
"Eyes in the head are characteristic of a great number of different animals, and essentially constitute a part of the plan of organisation of the vertebrates. Yet the mole, whose habits require a very small use of sight, has only minute and hardly visible eyes ...
Olivier's Spalax, which lives underground like the mole, and is apparently exposed to daylight even less than the mole, has altogether lost the use of sight: so that it shows nothing more than vestiges of this organ. Even these vestiges are entirely hidden under the skin and other parts, which cover them up and do not leave the slightest access to light.
The Proteus, an aquatic reptile allied to the salamanders, and living in deep dark caves under water, has, like the Spalax, only vestiges of the organ of sight, vestiges which are covered up and hidden in the same way." (Lamarck 1809, p. 116)
Even Aristotle discussed the peculiar vestigial eyes of moles in the fourth century B.C. in De animalibus historiae (lib. I cap. IX), in which he identified them as "stunted in development" and "eyes not in the full sense".
As these individuals noted, vestiges can be especially puzzling features of organisms, since these "hypocritical" structures profess something that they do not do—they clearly appear designed for a certain function which they do not perform. However, common descent provides a scientific explanation for these peculiar structures. Existing species have different structures and perform different functions. If all living organisms descended from a common ancestor, then both functions and structures necessarily have been gained and lost in each lineage during macroevolutionary history. Therefore, from common descent and the constraint of gradualism, we predict that many organisms should retain vestigial structures as structural remnants of lost functions. Note that the exact evolutionary mechanism which created a vestigial structure is irrelevant as long as the mechanism is a gradual one.
Confirmation:
There are many examples of rudimentary and nonfunctional vestigial characters carried by organisms, and these can very often be explained in terms of evolutionary histories. For example, from independent phylogenetic evidence, snakes are known to be the descendants of four-legged reptiles. Most pythons (which are legless snakes) carry vestigial pelvises hidden beneath their skin (Cohn 2001; Cohn and Tickle 1999). The vestigial pelvis in pythons is not attached to vertebrae (as is the normal case in most vertebrates), and it simply floats in the abdominal cavity. Some lizards carry rudimentary, vestigial legs underneath their skin, undetectable from the outside (Raynaud and Kan 1992).
Many cave dwelling animals, such as the fish Astyanax mexicanus (the Mexican tetra) and the salamander species Typhlotriton spelaeus and Proteus anguinus, are blind yet have rudimentary, vestigial eyes (Besharse and Brandon 1976; Durand et al. 1993; Jeffery 2001; Kos et al. 2001). The eyes of the Mexican tetra have a lens, a degenerate retina, a degenerate optic nerve, and a sclera, even though the tetra cannot see (Jeffery 2001). The blind salamanders have eyes with retinas and lenses, yet the eyelids grow over the eye, sealing them from outside light (Durand et al. 1993; Kos et al. 2001).
Dandelions reproduce without fertilization (a condition known as apomixis), yet they retain flowers and produce pollen (both are sexual organs normally used for sexual fertilization) (Mes et al. 2002). Flowers and pollen are thus useless characters for dandelions in terms of sexual reproduction.
There are many examples of flightless beetles (such as the weevils of the genus Lucanidae) which retain perfectly formed wings housed underneath fused wing covers. All of these examples can be explained in terms of the beneficial functions and structures of the organisms' predicted ancestors (Futuyma 1998, pp. 122-123).
The ancestors of humans are known to have been herbivorous, and molar teeth are required for chewing and grinding plant material. Over 90% of all adult humans develop third molars (otherwise known as wisdom teeth). Usually these teeth never erupt from the gums, and in one third of all individuals they are malformed and impacted (Hattab et al. 1995; Schersten et al. 1989). These useless teeth can cause significant pain, increased risk for injury, and may result in illness and even death (Litonjua 1996; Obiechina et al. 2001; Rakprasitkul 2001; Tevepaugh and Dodson 1995).
Another vestige of our herbivorous ancestry is the vermiform appendix. While this intestinal structure may retain a function of some sort, perhaps in the development of the immune system, it is a rudimentary version of the much larger caecum that is essential for digestion of plants in other mammals. For a detailed discussion of the vestigiality of the human vermiform appendix, see The vestigiality of the human vermiform appendix: A modern reappraisal.
Yet another human vestigial structure is the coccyx, the four fused caudal vertebrae found at the base of the spine, exactly where most mammals and many other primates have external tails protruding from the back. Humans and other apes are some of the only vertebrates that lack an external tail as an adult. The coccyx is a developmental remnant of the embryonic tail that forms in humans and then is degraded and eaten by our immune system (for more detail see the sections on the embryonic human tail and the atavistic human tail). Our internal tail is unnecessary for sitting, walking, and elimination (all of which are functions attributed to the coccyx by many anti-evolutionists). The caudal vertebrae of the coccyx can cause extreme and unnecessary chronic pain in some unfortunate people, a condition called coccydynia. The entire coccyx can be surgically removed without any ill effects (besides surgical complications), with the only complaint, in a small fraction of patients, being that the removal of the coccyx sadly did not remove their pain (Grossovan and Dam 1995; Perkins et al. 2003; Postacchini Massobrio 1983; Ramsey et al. 2003; Shaposhnikov 1997; Wray 1991). Our small, rudimentary, fused caudal vertebrae might have some minor and inessential functions, but these vertebrae are useless for balance and grasping, their usual functions in other mammals.
Potential Falsification:
No organism can have a vestigial structure that was not previously functional in one of its ancestors. Thus, for each species, the standard phylogenetic tree makes a huge number of predictions about vestigial characters that are allowed and those that are impossible for any given species.
Shared derived characters and molecular sequence data, not vestigial characters, determine the phylogeny and the characteristics of predicted common ancestors. Thus, if common descent is false, vestigial characters very possibly could lack an evolutionary explanation. For example, whales are classified as mammals according to many criteria, such as having mammary glands, a placenta, one bone in the lower jaw, etc. Snakes likewise are classified as reptiles by several other derived features. However, it is theoretically possible that snakes or whales could have been classified as fish (as Linnaeus originally did). If this were the case, the vestigial legs of whales or the vestigial pelvises of snakes would make no sense evolutionarily and would be inconsistent with common descent.
It follows, then, that we should never find vestigial nipples or a vestigial incus bone in any amphibians, birds, or reptiles. No mammals should be found with vestigial feathers. No primates should ever be found with vestigial horns or degenerate wings hidden underneath the skin of the back. We should never find any arthropods with vestigial backbones. Snakes may occasionally have vestigial legs or arms, but they should never be found with small, vestigial wings. Humans may have a vestigial caecum, since we are descendants of herbivorous mammals, but neither we nor any other primate can have a vestigial gizzard like that found in birds. Mutatis mutandis ad infinitum.
Criticisms:
This prediction is not falsified by finding a complex or essential function for the presumed vestigial structure. Should data of this sort be found, the structure merely becomes an example of parahomology (considered in prediction 3.1) or, more likely, an example of inefficient design (considered in prediction 3.5). Observations that would be truly inconsistent with the concept of vestigiality are given above. More detailed and specific explanations of how to demonstrate that the human appendix is not vestigial are given in the Vestigiality of the human vermiform appendix FAQ.
Many anti-evolutionist authors have erroneously concluded that vestigial structures do not exist. They reason that either (1) vestigial organs are actually functional or (2) it is theoretically impossible to demonstrate that a structure has no function (for example, see Ham et al. 1990; Batten and Sarfati 2003; Bergman and Howe 1990; Morris 1986). This latter argument is based upon the false premise that negative results are used to demonstrate a lack of function, and that negative evidence is unscientific. These arguments are faulty for three reasons, each discussed below.
- Vestiges can have functions
- Positive evidence demonstrates lack of functionality
- Negative evidence is scientific when controlled
1. Vestiges can be functional
First, and most importantly, this line of argumentation is beside the point, since it is unnecessary for vestiges to lack a function (see Muller 2002 for a modern discussion of the vestigial concept that specifically includes functionality). Many true vestiges are functional (for many examples see Culver et al. 1995). In popular usage "vestigial" is often believed to be synonymous with "nonfunctional", and this confusion unfortunately has been propagated via poorly-worded definitions found in many non-technical dictionaries and encyclopedias. Even some professional research biologists have fallen prey to this oversimplification of the vestigial concept (for instance, Scadding 1981, often quoted by anti-evolutionists and discussed in the Citing Scadding (1981) and Misunderstanding Vestigiality FAQ). The statement that vestigial structures are functionless is a convenient, yet strictly incorrect, approximation. It is analogous to the common, yet strictly incorrect, scientific claim that the earth is a sphere.
Several evolution deniers have falsely claimed that biologists changed the definition of vestigial and rudimentary structures when functions were found for many vestiges (see Bergman and Howe 1990, pp. 2-3; Sarfati, J. 2002). For example, Answers in Genesis' Jonathan Sarfati states:
Historical definitions of 'Vestigial' including functionality
See quotes at left from Darwin 1859 and 1872, Weismann 1886, and Wiedersheim 1893.
vestigial. a. Of, pertaining to, or of the nature of a vestige; like a mere trace of what has been; also, rudimentary. In biology vestigial has a specific application to those organs or structures which are commonly called rudimentary, and are rudimentary in fact, but which are properly regarded, not as beginnings or incipient states, but as remains of parts or structures which have been better developed in an earlier stage of existence of the same organismm, or in lower preceding organisms, and have aborted or atrophied, or become otherwise reduced or rudimental in the evolution of the individual or of the species.
(The Century Dictionary: An Encyclopedic Lexicon of the English Language 1911)"Vestigial organs are sometimes pressed into a secondary use when their original function has been lost."
(The Story of Evolution, Joseph McCabe, 1912, p.264)vestige b. (biol.) a rudimentary, degenerate survival of a former organ or structure.
(Universal Dictionary of the English Language 1932)vestige n. 2. Biol Specif., a small, degenerate, or imperfectly developed part or organ which has been more fully developed in an earlier stage of the individiual or in a past generation.
(Webster's New International Dictionary of the English Language 1957)When structures undergo a reduction in size together with a loss of their typical function, that is, when they become vestigial, they are quite commonly considered to be degenerate and functionless. But Simpson has recently pointed out that this need not be true at all: the loss of the original function may be accompanied by specialization for a new function.
(Evolution: Process and Product, E. O. Dodson, 1960)vestige. n. 2: a small and degenerate or imperfectly developed bodily part or organ that remains from one more fully developed in an earlier stage of the individual, in a past generation, or in closely related forms.
(Webster's Seventh New Collegiate Dictionary 1963)vestige. n. 2. Biol. A part or organ small or degenerate, tho ancestrally well developed.
vestigial adj. Biol. Having become small or degenerate: representing a structure or structures once more complete in functional activity.
(Funk and Wagnalls New Standard Dictionary of the English Language 1964)"It is incorrect to state that to be vestigial an organ must be non-functional ... it is not essential that a vestigial organ be totally without function."
(Naylor 1982)vestige A degenerate anatomical structure or organ that remains from one more fully developed and functional in an earlier phylogenetic form of the individual.
(Dictionary of Bioscience 1997)vestigial Occuring in a rudimentary condition, as a result of evolutionary reduction from a more elaborated, functional character state in an ancestor.
( Futuyma 1998, from the Glossary)Vestigial Organs and Structures
Vestigial organs and structures (also called vestigia, rudiments, or remnants) are reduced body parts or organs, often without visible function in the derived bearers, that were fully developed and functioning in earlier members of that phylogenetic lineage. These structures, sometimes described as atrophied or degenerate, are usually small in comparison with their relative size in ancestral generations or in closely related species. ... vestigial structures may have acquired new, less obvious functions that differ from the original ones. Hence, a vestigium should not generally be considered without function, or only with respect to its ancestral, adult roles.
(Encyclopedia of Evolution 2002, pp 1131-1133)vestige noun 2: a bodily part or organ that is small and degenerate or imperfectly developed in comparison to one more fully developed in an earlier stage of the individual, in a past generation, or in closely related forms.
( Merriam-Webster Dictionary 2003)
" The World Book Encyclopedia 2000 says: 'Vestigial organs are the uselessremains of organs that were once useful in an evolutionary ancestor' (emphasis added). ... Some evolutionists, like Dr Meiss, now want to re-define 'vestigial' to mean simply 'reduced or altered in function'. ... AiG isn't going to let evolutionists change the rules at their whim when they are losing the argument." (Sarfati, J. 2002). "The Shorter Oxford English Dictionary (1993) defines 'vestigial' as 'degenerate or atrophied, having become functionless in the course of evolution.' Some evolutionists now re-define 'vestigial' to mean simply 'reduced or altered in function.' Thus even valuable, functioning organs (consistent with design) might now be called 'vestigial.' Creationists should not let evolutionists change the rules when they lose." (Sarfati, J. 1999). Sarfati's arguments are invalid for several reasons.
First, even if biologists truly had changed the definition of 'vestige', why would that be a problem in science? It would not—all science changes as new data is acquired and theories become clarified. Using Sarfati's logic we would reject modern theories like Einstein's theory of relativity, since "physicists changed the rules at whim when they lost".
Second, Sarfati quotes terse, layman's definitions from a popular dictionary and a children's encyclopedia as if they were scientific authorities. It is highly likely that the person who wrote those definitions was not an evolutionary biologist. For all we know, it even may have been an anti-evolutionist or young earth creationist! Any true scientist (or legitimate scholar of any sort) would consult an advanced scientific text for definitions of technical terms, especially when attempting to criticize them. In this case, the two-volume Encyclopedia of Evolution (Muller 2002), with technical discussions written by real practicing research biologists, would be one of many appropriate sources.
Third, regardless of popular misconception, from the beginning of modern evolutionary theory a complete absence of function has not been a requirement for vestigiality (Crapo 1985; Culver et al. 1995; Darwin 1872, pp. 601-609; Dodson 1960, p. 44; Griffiths 1992; McCabe 1912, p. 264; Merrell 1962, p. 101; Moody 1962, p. 40; Muller 2002; Naylor 1982; Strickberger 2000; Weismann 1886; Wiedersheim 1893, p. 2, p. 200, p. 205). Sarfati's claim is based upon ignorance, and he of course provides no historical references showing that evolutionary biologists actually changed the definition. As an obvious counterexample, Charles Darwin never claims vestigial organs must be functionless. In his famous section on vestigial organs in On the Origin of Species, written nearly 150 years ago, Darwin in fact emphasizes that vestiges can be functional and gives several examples:
"Useful organs, however little they may be developed, unless we have reason to suppose that they were formerly more highly developed, ought not to be considered as rudimentary." (Darwin 1859, emphasis added)
"An organ, serving for two purposes, may become rudimentary or utterly aborted for one, even the more important purpose, and remain perfectly efficient for the other. Thus, in plants, the office of the pistil is to allow the pollen-tubes to reach the ovules protected in the ovarium at its base. The pistil consists of a stigma supported on the style; but in some Compositae, the male florets, which of course cannot be fecundated, have a pistil, which is in a rudimentary state, for it is not crowned with a stigma; but the style remains well developed, and is clothed with hairs as in other compositae, for the purpose of brushing the pollen out of the surrounding anthers. Again, an organ may become rudimentary for its proper purpose, and be used for a distinct object: in certain fish the swim-bladder seems to be rudimentary for its proper function of giving buoyancy, but has become converted into a nascent breathing organ or lung. Other similar instances could be given." (Darwin 1859 [see text]; also Darwin 1872, p. 602, emphasis added)
"Rudimentary organs, on the other hand, are either quite useless, such as teeth which never cut through the gums, or almost useless, such as the wings of an ostrich, which serve merely as sails." (Darwin 1872, p. 603)
"... an organ rendered, during changed habits of life, useless or injurious for one purpose, might easily be modified and used for another purpose." (Darwin 1872, p. 603)
One of the most influential evolutionary biologists of the 19th century, August Weismann, wrote on functional vestiges in 1886 in his lengthy essay, "Retrogressive development in nature":
"... for, although the latter [ostrich] does not fly, it still uses its wings as aids in running swiftly over the African plains and deserts ... Retrogression is, however, not always carried so far as to do away with a structure altogether ... But not infrequently the degenerating organ can be turned to account in some other way, and then retrogression either stops just short of actual elimination, as in the case of the wings of the ostrich, or so alters and transforms the structure as to fit it for new functions ..." (Weismann 1886, pp. 5-9)
As explained above, what is surprising about the functional, vestigial ostrich wing is not that the ostrich wing lacks any function whatsoever, but that it is a rudimentary wing unused for powered flight, its "proper purpose", as Darwin puts it. Even Robert Wiedersheim, the notorious cataloguer of 86 human vestigial structures, never claims that vestigial structures must lack functions. In the introduction to The Structure of Man, Wiedersheim defines "vestigial" in evolutionary terms:
"Comparative morphology points not only to the essentially similar plan of organization of the bodies of all Vertebrates, ... but also to the occurrence in them of certain organs, or parts of organs, now known as 'vestigial.'
By such organs are meant those which were formerly of greater physiological significance than at present." (Wiedersheim 1893, p. 2)
At the end of his book, Wiedersheim lists his 86 vestigial structures under this heading:
"B. Retrogressively modified, the Organs having become wholly or in part functionless, some appearing in the Embryo alone, others present during Life constantly or inconstantly. For the greater part Organs which may be rightly termed Vestigial." (Wiedersheim 1893, p. 200, emphasis added) "... as was pointed out in the introduction, the term vestigial, is, as a rule, only applied to such organs as have lost their original physiological significance." (Wiedersheim 1893, p. 205) Wiedersheim, writing from an evolutionary perspective, emphasizes in his definition that vestigial structures have lost their original, greater physiological significance, not all physiological significance. He never limits vestigial structures to those lacking a function and throughout the book mentions functions of many organs he labels as vestigial.
Many anti-evolutionists enjoy quoting a paper by Steven Scadding (Scadding 1981) in which he criticizes Wiedersheim's analysis of vestigial organs as evidence for evolution. Scadding's objections are based upon the false premise that vestigial structures must have no function by definition. Wiedersheim, whom Scadding is criticizing specifically, does not make that claim. Since Scadding misrepresents Wiedersheim's position and uses an incorrect definition of vestigial in general, Scadding's points are invalid. The deep problems with Scadding's paper have been corrected in the scientific literature, and anti-evolutionists who quote this paper are engaging in poor scholarship. A detailed discussion of Scadding's 1981 paper is given in the Citing Scadding (1981) and Misunderstanding Vestigiality FAQ.
![[Figure2.1.1 (ostrich with wings extended)]](http://www.talkorigins.org/faqs/comdesc/images/ostrich.jpg)
![[Figure2.1.1 (blind cave salamander)]](http://www.talkorigins.org/faqs/comdesc/images/blind_salamander.jpg)
![[Figure2.1.1 (blind cave fish, the Mexican tetra)]](http://www.talkorigins.org/faqs/comdesc/images/Mexican_tetra.jpg)
![[Figure2.1.2 (flightless weevil, apterocyclus_honolulensis)]](http://www.talkorigins.org/faqs/comdesc/images/flightless_weevil.jpg)
![[Figure2.1.2 (vestigial dandelion]](http://www.talkorigins.org/faqs/comdesc/images/dandelion.jpg)
![[Figure2.1.2 (vestigial dandelion pollen)]](http://www.talkorigins.org/faqs/comdesc/images/dandelion_pollen.jpg)
