A vestigial organ is an organ whose original function is considered to have been lost or reduced during evolution. In 1893, Robert Wiedersheim published a list of 86 human organs that had no known function. Theorizing that they were vestiges of evolution, he called them "vestigial". In biology, an organ (Latin: organum, instrument, tool) is a group of tissues, which perform a specific function or group of functions. ... A speculatively rooted phylogenetic tree of all living things, based on rRNA gene data, showing the separation of the three domains, bacteria, archaea, and eukaryotes, as described initially by Carl Woese. ... 1893 was a common year starting on Sunday (see link for calendar). ...

Today, the list of human vestigial organs is still the same, although the list of useless vestigial organs is much smaller, and hotly debated. It still includes the appendix, and coccyx. Many people maintain that the coccyx is a remnant of a lost tail. Wisdom teeth are vestigial as well. Also, the plica semilunaris, the small fold of tissue on the inside corner of the eye, is the vestigial remnant of the nictitating membrane (the third eyelid) in other animals. In human anatomy, the vermiform appendix (or appendix, pl. ... The coccyx is formed of four fused vertebrae. ... Wisdom teeth are third molars that usually appear between the ages of 18 and 20 (although they may appear when older, or fail to appear at all). ... Many species of land animals have a nictitating membrane, sometimes (but incorrectly) spelled nicitating membrane, which can move across the eyeball to give the sensitive eye structures additional protection in particular circumstances. ...

The formation of goose bumps in humans under emotional stress is a vestigial reflex; its purpose in our evolutionary ancestors was to raise hair to make the animal appear bigger and scare off enemies, although they were more likely used to trap an insulating of layer of warm air next to the skin. Goose bumps on a human Goose bumps (AE), also called goose pimples, goose flesh (BE), chicken skin (Hawaiian Pidgin), or cutis anserina, are the bumps on a persons skin at the base of body hairs which involuntarily develop when a person is cold or experiences strong emotions like fear. ... A reflex action or reflex is a biological control system linking stimulus to response and mediated by a reflex arc. ...

Some traits may be vestigial in one sex but not another because they are homologous but do not share similar functions between the sexes. Organs with a distinct purpose in one sex, for example the nipple, may be more or less useless in the other, but not harmful enough to be selected against. These become vestigial traits in one sex. The clitoris has been described as a vestigial penis by some scientists, such as Stephen Jay Gould. Others argue that the clitoris serves an important reproductive function in female orgasm. Wikimedia Commons has media related to: Sex positions Francoeur, Robert T. (ed. ... Two or more structures are said to be homologous if they are alike because of shared ancestry. ... Nipple is, generally, the name given to the mammalian nipple. ... A womans clitoris extends from the visible portion to a point below the pubic bone. ... The penis (plural penises or penes) is in addition to the scrotum one of the external male sexual organs. ... Stephen Jay Gould For the science fiction writer, see Steven Gould. ... An orgasm, also known as a sexual climax, is an intensely pleasurable physical, psychological or emotional response to prolonged sexual stimulation. ...

In whales and other cetaceans, one can find small vestigial leg bones deeply buried within the body; these are remnants of their land-living ancestors' legs. The wings of ostriches and emus are vestigial, remnants of their flying ancestors' wings. Whales are the largest species of exclusively aquatic mammals, members of the order Cetacea, which also includes dolphins and porpoises. ... Suborders Mysticeti Odontoceti (see text) The order Cetacea includes whales, dolphins and porpoises. ... Binomial name Struthio camelus Linnaeus, 1758 The ostrich (Struthio camelus) is a flightless bird native to Africa. ... The abbreviation EMU is an acronym with multiple uses. ...

Some debate occurs regarding the definition for "vestigial", with some claiming a strict interpretation that an organ must be utterly useless to classify. Others claim that an organ in a modern animal may be described 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. 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. In biology, two or more structures are said to be homologous if they are alike because of shared ancestry. ... Preadaptation describes a situation where an organism uses a preexisting anatomical structure inherited from an ancestor for a potentially unrelated purpose. ... 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 waste energy in swimming. ... The lungs flank the heart and great vessels in the chest cavity. ... Orders See text The Actinopterygii are the ray-finned fish. ...

Because vestigial organs can be used as supporting evidence for evolution, some creationists oppose the idea. A speculatively rooted phylogenetic tree of all living things, based on rRNA gene data, showing the separation of the three domains, bacteria, archaea, and eukaryotes, as described initially by Carl Woese. ... This article is about the Abrahamic belief; creationism can also refer to origin beliefs in general or, centuries earlier, to an alternative to traducianism. ...

Definition

Organs or structures remaining or surviving in a degenerate, atrophied, or imperfect condition or form.

External links

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