The human vermiform appendix is a vestigial structure; it no longer retains its original function.

Vestigial structures are anatomical structures of organisms in a species, which have lost much or all of their original function through evolution. They are typically in a degenerate, atrophied, or rudimentary condition. They are often called vestigial organs, although not all of them are actually organs. Image File history File links Gray536. ... Image File history File links Gray536. ... In human anatomy, the vermiform appendix (or appendix, pl. ... Anatomical drawing of the human muscles from the Encyclopédie. ... This article or section does not cite any references or sources. ... In biology, a species is one of the basic units of biodiversity. ... This article is about evolution in biology. ... In biology, an organ (Latin: organum, instrument, tool) is a group of tissues that perform a specific function or group of functions. ...

Although structures usually called "vestigial" are largely or entirely functionless, a vestigial structure may retain lesser functions or develop new ones.^[1] Thus, a "vestigial wing" is one useless for flight, but may serve some other purpose.

History

The blind mole rat (Spalax typhlus) has tiny eyes completely covered by a layer of skin.

Vestigial structures have been noticed since ancient times, and the reason for their existence was long speculated upon before Darwinian evolution provided a widely-accepted explanation. In the 4th century BC, Aristotle was one of the earliest writers to comment, in his History of Animals, on the vestigial eyes of moles, calling them "stunted in development".^[2] However, only in recent centuries have anatomical vestiges become a subject of serious study. In 1798, Étienne Geoffroy Saint-Hilaire noted on vestigial structures: Image File history File links Download high resolution version (1554x948, 381 KB) Original caption: Blindmaus, Spalax typhlus Pall. ... Image File history File links Download high resolution version (1554x948, 381 KB) Original caption: Blindmaus, Spalax typhlus Pall. ... Genera Nannospalax Spalax Blind mole rats are one of many types of rodents that are referred to as mole rats. ... This article is about biological evolution. ... Aristotle (Greek: AristotélÄ“s) (384 BC – March 7, 322 BC) was a Greek philosopher, a student of Plato and teacher of Alexander the Great. ... History of Animals (or Historia Animalium, or On the History of Animals) is a text by Aristotle. ... An engraving of Étienne Geoffroy Saint-Hilaire. ...

His colleague, Jean-Baptiste Lamarck, named a number of vestigial structures in his 1809 book Philosophie Zoologique. Lamarck noted "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."^[4] This article or section is in need of attention from an expert on the subject. ... Jean-Baptiste Lamarck. ... Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (August 1, 1744 - December 28, 1829) was a major 19th century naturalist, who was one of the first to use the term biology in its modern sense. ... Guillaume-Antoine Olivier (1756 - 1814) was a French entomologist. ... Genera Nannospalax Spalax Blind mole rats are one of many types of rodents that are referred to as mole rats. ...

Charles Darwin was very familiar with the concept of vestigial structures, though the term for them did not yet exist. He listed a number of them in The Descent of Man, including the muscles of the ear, wisdom teeth, the appendix, the tail bone, body hair, and the semilunar fold in the corner of the eye. Darwin also noted, in The Origin of Species, that a vestigial structure could be useless for its primary function, but still retain secondary anatomical roles: "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.... [A]n organ may become rudimentary for its proper purpose, and be used for a distinct object."^[5] For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... Title page of the first edition of Charles Darwins The Descent of Man, and Selection in Relation to Sex. ... The intrinsic muscles are the: The Helicis major is a narrow vertical band situated upon the anterior margin of the helix. ... Wisdom teeth are third molars that usually appear between the ages of 17 and 24 (although they may appear when older, younger, or may not appear at all). ... In human anatomy, the vermiform appendix (or appendix, pl. ... The coccyx, commonly referred to as the tailbone, is the final segment of the human vertebral column, of three to five (usually four) fused vertebrae (the coccygeal vertebrae), below the sacrum. ... Hair is also a musical: see Hair (musical) and Hair (movie) Hair is the filamentous outgrowth of the epidermis found in mammals. ... Many species of land animals have a nictitating membrane, which can move across the eyeball to give the sensitive eye structures additional protection in particular circumstances. ... This article refers to the sight organ. ... British naturalist Charles Darwins book, The Origin of Species, is one of the pivotal works in scientific literature and arguably the pre-eminent work in biology. ...

Darwin however still often refers to the use and disuse of structures having some role in heredity, which mixes a form of Lamarckism with the theory of natural selection. In the final chapter of The Origin of Species he describes the process: "This has been effected chiefly through the natural selection of numerous successive, slight, favourable variations; aided in an important manner by the inherited effects of the use and disuse of parts".^[5] Lamarckism or Lamarckian evolution is a theory put forward by the French biologist Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck, based on heritability of acquired characteristics, the once widely accepted idea that an organism can acquire characteristics during its lifetime and pass them on to its offspring. ...

In 1893, Robert Wiedersheim published a list of 86 human organs that had, in his words, "lost their original physiological significance". Theorizing that they were vestiges of evolution, he called them "vestigial".^[6] Since his time, the function of some of these structures has been discovered, while other anatomical vestiges have been unearthed, making the list primarily of interest as a record of the knowledge of human anatomy at the time. Later versions of Wiedersheim's list were expanded to as many as 180 human "vestigial organs". This is why the zoologist Newman stated in the Scopes Monkey Trial that "There are, according to Wiedersheim, no less than 180 vestigial structures in the human body, sufficient to make of a man a veritable walking museum of antiquities."^[7] Robert Wiedersheim (1848 – 1932) was a German anatomist who is famous for publishing a list of 86 “vestigial organs” in 1893. ... The Scopes Trial of 1925 pitted William Jennings Bryan against Clarence Darrow and teacher John T. Scopes in an American court case that tested a law passed on March 13, 1925, forbidding the teaching of evolution in Tennessee public schools. ...

Evidence of evolution

Main article: Evidence of evolution

Vestigial structures are often homologous to structures that are functioning normally in other species. Therefore, vestigial structures can be considered evidence for evolution, the process by which beneficial heritable traits arise in population over an extended period of time. The existence of vestigial organs can be attributed to changes in the environment and behavior patterns of the organism in question. As the function of the structure is no longer beneficial for survival, the likelihood that future offspring will inherit the "normal" form of the structure decreases. In some cases the structure becomes detrimental to the organism (for example the eyes of a mole can become infected^[5]). In many cases the structure is of no direct harm, yet all structures require extra energy to build and maintain, providing some selective pressure for the removal of parts that do not contribute to an organism's fitness. A structure that is not harmful will obviously take longer to be phased out than one that is. While on board HMS Beagle, Charles Darwin collected numerous specimens, many new to science, which supported his later theory of evolution by natural selection. ... In biology, homology is any similarity between structures that is due to their shared ancestry. ... This article is about evolution in biology. ... Darwins illustrations of beak variation in the finches of the Galápagos Islands, which hold 13 closely related species that differ most markedly in the shape of their beaks. ...

The vestigial versions of the structure can be compared to the original version of the structure in other species in order to determine the homology of a vestigial structure. Homologous structures indicate common ancestry with those organisms that have a functional version of the structure.^[8]

In humans

The muscles connected to the ears of a human do not develop enough to have the same mobility allowed to monkeys.

Although the list of human vestigial structures is still more or less the same, the relative usefulness of certain structures on the list is a subject of debate. The following are some of the structures often included in this list: Image File history File links Download high resolution version (1011x706, 113 KB) Derived by LP from Image:Ear_with_earring. ... Image File history File links Download high resolution version (1011x706, 113 KB) Derived by LP from Image:Ear_with_earring. ...

The vermiform appendix is a vestige of the cecum, an organ that may have been used to digest cellulose by humans' herbivorous ancestors.^{[citation needed]} Analogous organs in other animals similar to humans continue to perform that function, whereas other meat-eating animals may have similarly diminished appendices. The modern functionality of the appendix is still controversial in the field of human physiology, although most scientists and physicians believe that it has little or no function. In human anatomy, the vermiform appendix (or appendix, pl. ... The cecum or caecum (from the Latin caecus meaning blind) is a pouch connected to the ascending colon of the large intestine and the ileum. ...

The coccyx, or tailbone, is the remnant of a lost tail. All mammals have a tail at one point in their development; in humans, it is present for a short time during embryonic development. The tailbone, located at the end of the spine, has lost its original function in assisting balance and mobility, though it still serves some secondary functions, such as being an attachment point for muscles, which explains why it has not degraded further. In rare cases it can persist after birth and must be surgically removed. The coccyx is formed of up to five vertebrae. ... A scorpion tail A tail is the section at the rear end of an animals body, the term particularly referring to such a section which forms a distinct, flexible appendage to the torso. ... It has been suggested that embryology be merged into this article or section. ...

The plica semilunaris is small fold of tissue on the inside corner of the eye. It is the vestigial remnant of the nictitating membrane (the "third eyelid") which is present in other animals. The plica semilunaris is small fold of tissue on the inside corner of the eye. ... Many species of land animals have a nictitating membrane, which can move across the eyeball to give the sensitive eye structures additional protection in particular circumstances. ...

Wisdom teeth are vestigial third molars that human ancestors used to help in grinding down plant tissue. It has been postulated that the skulls of human ancestors had larger jaws with more teeth, which were possibly used to help chew down foliage to compensate for a lack of ability to efficiently digest the cellulose that makes up a plant cell wall. As human diet changed, a smaller jaw was selected by evolution, yet the third molars, or "wisdom teeth", still commonly develop in human mouths.^[9] Wisdom teeth are third molars that usually appear between the ages of 17 and 24 (although they may appear when older, younger, or may not appear at all). ... Cellulose as polymer of β-D-glucose Cellulose in 3D Cellulose (C6H10O5)n is a polysaccharide of beta-glucose. ... Selection is hierachically classified into natural and artificial selection. ...

Goose bumps are an example of a vestigial human reaction to stress.

Humans also bear some vestigial behaviors and reflexes. For example, the formation of goose bumps in humans under stress is a vestigial reflex; its purpose in human evolutionary ancestors was to raise the body's hair, making the ancestor appear larger and scaring off predators. Raising the hair is also used to trap an extra layer of air, keeping an animal warm. This reflex formation of goosebumps when cold is not vestigial in humans, but the reflex to form them under stress is. Image File history File links Size of this preview: 420 × 599 pixel Image in higher resolution (561 × 800 pixel, file size: 90 KB, MIME type: image/jpeg) La bildo estas kopiita de wikipedia:de. ... Image File history File links Size of this preview: 420 × 599 pixel Image in higher resolution (561 × 800 pixel, file size: 90 KB, MIME type: image/jpeg) La bildo estas kopiita de wikipedia:de. ... Goose bumps on a human Goose bumps (AE), also called goose pimples, goose flesh (BE), chill bumps, chicken skin (Hawaiian Pidgin), or the medical term cutis anserina, are the bumps on a persons skin at the base of body hairs which involuntarily develop when a person is cold or... Goose bumps, also called goose pimples, goose flesh, or cutis anserina, are the bumps on a persons skin at the base of body hairs (typically on the forearm), which involuntarily develop when a person is cold, afraid, or experiences other strong emotions. ... In medical terms, stress is a physical or psychological stimulus that can produce mental or physiological reactions that may lead to illness. ... The mechanism of the reflex arc. ...

The ears of a Macaque monkey, and most other monkeys, have far more developed muscles than those of humans and therefore have the capability to move their ears to better hear potential threats.^[10] In humans, the inability to move the ear is compensated mainly by the ability to turn the head on a horizontal plane, an ability which is not common to most monkeys. A function once provided by one structure is now replaced by another.^[11] Type species Simia inuus Linnaeus, 1758 = Simia sylvanus Linnaeus, 1758 Species See text. ...

There are also vestigial molecular structures in humans, which are no longer in use but may indicate common ancestry with other species. One example of this is L-gulono-gamma-lactone oxidase, a gene, found functional in most other mammals, which produces a Vitamin C-catalyzing enzyme. In humans, an earlier mutation may have caused it to become disabled (unable to produce the enzyme), and it now remains in the human genome only as a vestigial genetic sequence.^[12] For other uses, see Vitamin C (disambiguation). ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... A graphical representation of the normal human karyotype. ...

In other organisms

Letter c in the picture indicates the undeveloped hind legs of a baleen whale.

In whales and other cetaceans, one can find small vestigial leg bones deeply buried within the back of the body. These are remnants of their land-living ancestors' legs. Many whales also have undeveloped, unused, pelvis bones in the anterior part of their torsos. Image File history File links Skelett_vom_Wal_MK1888_ohne_Text. ... Image File history File links Skelett_vom_Wal_MK1888_ohne_Text. ... Families Balaenidae Balaenopteridae Eschrichtiidae Neobalaenidae Scientifically known as the Mysticeti, the baleen whales, also called whalebone whales or great whales, form a suborder of the order cetacea. ... A Fin Whale The term whale is ambiguous: it can refer to all cetaceans, to just the larger ones, or only to members of particular families within the order Cetacea. ... Suborders Mysticeti Odontoceti (see text) The order Cetacea includes whales, dolphins and porpoises. ... The pelvis (pl. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ...

Dodo birds (now extinct) have hollow bones, a feature usually reserved for flying birds. (The weight reduction is crucial to staying in the air. Since Dodo birds did not fly, having hollow bones was unneeded, and likely vestigial.^[13]) The wings of ostriches, emus, and other flightless birds are vestigial; they are remnants of their flying ancestors' wings. Binomial name Raphus cucullatus (Linnaeus, 1758) Former range (in red) Synonyms Struthio cucullatus Linnaeus, 1758 Didus ineptus Linnaeus 1766 Probably the earliest accurate drawings of a dodo (1601-1603). ... Binomial name Struthio camelus Carolus Linnaeus, 1758 The present-day distribution of Ostriches. ... Binomial name Dromaius novaehollandiae (Latham, 1790) The Emu has been recorded in the areas shown in black. ... Flightless birds evolved from flying ancestors; there are about forty species in existence today. ...

The eyes of certain cavefish and salamanders are vestigial, as they no longer allow the organism to see, and are remnants of their ancestors' functional eyes. Genera  Amblyopsis  Chologaster  Forbesichthys  Speoplatyrhinus  Typhlichthys The cavefishes are a family Amblyopsidae of fish found in caves and adapted to life in the dark, notably lacking eyes and of a pale or white color. ... Suborders Cryptobranchoidea Salamandroidea Sirenoidea Salamander is the common name applied to approximately 500 amphibians with slender bodies, short legs, and long tails. ...

Crabs have small tails tucked between their rear legs that are probably vestigial, as they are no longer in use. The working version of these tails can be found in their close crustacean relative, the lobster.^[13] Phthirus pubis Pubic lice (Phthirus pubis), also known as crabs , are one of the many varieties of lice (singular louse) specialized to live on different areas of different animals. ... Classes & Subclasses Branchiopoda Phyllopoda Sarsostraca Remipedia Cephalocarida Maxillopoda Thecostraca Tantulocarida Branchiura Pentastomida Mystacocarida Copepoda Ostracoda Myodocopa Podocopa Malacostraca Phyllocarida Hoplocarida Eumalacostraca The nauplius larva of a dendrobranchiate Porcellio scaber, the common rough woodlouse, a terrestrial crustacean Pollicipes polymerus, the gooseneck barnacle Glyphea pseudastacus, a fossil glypheoid The crustaceans (Crustacea) are... Subfamilies and Genera Neophoberinae Acanthacaris Thymopinae Nephropsis Nephropides Thymops Thymopsis Nephropinae Homarus Nephrops Homarinus Metanephrops Eunephrops Thymopides Clawed lobsters comprise a family (Nephropidae, sometimes also Homaridae) of large marine crustaceans. ...

Vestigial structures are not only found in animals; plants also are known to have vestigial parts. Dandelions and other asexually reproducing plants produce unneeded flower petals. These petals were once used to attract pollinating insects, but are now no longer needed.^[13] Species Taraxacum officinale Taraxacum japonicum Taraxacum albidum and a few others. ... It has been suggested that Parthenogenesis be merged into this article or section. ...

Grass often has small, undeveloped structures which strongly resemble those of flowering plants.^[13] Natural vegetation dominated by grasses Grass is a common word that generally describes a monocotyledonous green plant in the family Poaceae. ...

Certain species of moths (for example the Gypsy moth) have females that although flightless, still carry small wings. These wings have no use, and are vestigial to the versions in species whose females can fly.^[13] Lepidopteran on a flower. ... Binomial name Lymantria dispar Linnaeus, 1758 The gypsy moth, Lymantria dispar, is a moth in the family Lymantriidae of Eurasian origin. ...

The fruit fly can be bred in high school experiments to produce off-spring with vestigial wings, to better understand basic genetics in biology. Fruit fly may refer to: Tephritidae, the family of large fruit flies. ...

Controversy

Because vestigial organs are used as supporting evidence for evolution, some creationists oppose the validity of the idea. They question whether these organs are useless, since they believe that gods or God gave each organism its organs for a specific reason and use. Other creationists allow for "micro-evolution" (variations in individual species) but not "macro-evolution" (all species originating from common ancestors). Vestigial structures do not oppose the beliefs of this branch of creationism. This article is about evolution in biology. ... Creationism is the belief that humanity, life, the Earth, and the universe were created in their entirety by a supernatural deity or deities (typically God), whose existence is presupposed. ... This article discusses the term God in the context of monotheism and henotheism. ...

Those who question the existence of vestigial organs usually claim a different definition for vestigial, giving a strict interpretation that an organ must be utterly useless to qualify.^[14] This is a definition often used in dictionaries^[15] and children's encyclopedias.^[16] Biology textbooks^[17][18] and scientific encyclopedias^[1] usually describe an organ as vestigial if it does not serve the same function in the modern animal as the cognate organ served in an ancestor, even if the modern organ serves a completely different use (preadaptation). In biology, homology is any similarity between structures that is due to their shared ancestry. ... In evolutionary biology, preadaptation describes a situation where an organism uses a preexisting anatomical structure inherited from an ancestor for a potentially unrelated purpose. ...

Those who consider the true meaning of vestigial to be "completely without use" tend to claim that the meaning has been changed over time as structures thought to be vestigial were found to have other uses.^[19] However, documentation indicates that from the theory's beginnings in the 19th century, vestigial structures have invariably been understood to "sometimes retain their potentiality"^[20], becoming either "wholly or in part functionless".^[21] It was thought that "not infrequently the degenerating organ can be turned to account in some other way".^[22]

An example of the dispute is the gas bladder of many fish, which is thought to be a vestigial lung, "left over" from the occasionally-air-gasping common ancestor of ray-finned fish and land vertebrates. The gas bladder of a Rudd The gas bladder (also fish maw, less accurately swim bladder or air bladder) is an internal organ that contributes to the ability of a fish to control its buoyancy, and thus to stay at the current water depth, ascend, or descend without having to... Image:3DScience respiratory labeled. ... Orders See text The Actinopterygii are the ray-finned fish. ...

See also

• Dewclaw
• Plantaris muscle
• Atavism
• Dandelion

PinkieS! The dogs front dewclaw grows on the side of the foot, above the other four toes but below the rear heelpad. ... The Plantaris muscle is a muscle of the human body. ... An atavism can mean an organism that is a real or supposed evolutionary throwback; the unexpected appearance of primitive traits; or a reversion to or reappearance of a trait that had been present in a lineage in the past, but which had been absent in intervening generations. ... Species See text A dandelion is a short plant, usually with a yellow flower head and notched leaves. ...

References

Aristotle (Greek: Aristotélēs) (384 BC – March 7, 322 BC) was a Greek philosopher, a student of Plato and teacher of Alexander the Great. ... An engraving of Étienne Geoffroy Saint-Hilaire. ... Jean-Baptiste Lamarck. ... Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (August 1, 1744 - December 28, 1829) was a major 19th century naturalist, who was one of the first to use the term biology in its modern sense. ... For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... British naturalist Charles Darwins book, The Origin of Species, is one of the pivotal works in scientific literature and arguably the pre-eminent work in biology. ... Robert Wiedersheim (1848 – 1932) was a German anatomist who is famous for publishing a list of 86 “vestigial organs” in 1893. ...

External links

• Article relating to vestigial clitoris controversy
• Talk origins page on vestigial organs