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". His colleague, Jean-Baptiste Lamarck , named a number of vestigial structures in his 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.
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 Darwin however still often refers to the 'use and disuse' of structures having some role in heredity, with inheritance of acquired characters being treated as an important aspect besides the central force of natural selection.
In , 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". Later versions of Wiedersheim's list were expanded to as many as human "vestigial organs". This is why the zoologist Newman stated in the Scopes Monkey Trial that "There are, according to Wiedersheim, no less than vestigial structures in the human body, sufficient to make of a man a veritable walking museum of antiquities.
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 populations over an extended period of time.
The existence of vestigial traits can be attributed to changes in the environment and behavior patterns of the organism in question.
As the function of the trait is no longer beneficial for survival, the likelihood that future offspring will inherit the "normal" form of it 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 in terms of development, maintenance, and weight, and are also a risk in terms of disease e. A structure that is not harmful will obviously take longer to be 'phased out' than one that is. However, some vestigial structures may persist due to limitations in development, such that complete loss of the structure could not occur without major alterations of the organism's developmental pattern, and such alterations would likely produce numerous negative side-effects.
The toes of many animals such as horses , who stand on a single toe , are still evident in a vestigial form and may become evident, although rarely, from time to time in individuals. 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. Vestigial traits are still considered adaptations. This is because an adaptation is defined as a trait that has been favored by natural selection. Adaptations therefore need not be adaptive , as long as they were at some point.
In whales and other cetaceans , one can find small vestigial leg bones deeply buried within the back of the body. Many whales also have undeveloped, unused, pelvis bones in the anterior part of their torsos. Therefore, vestigial structures can be considered evidence for evolution, the process by which beneficial heritable traits arise in populations over an extended period of time.
The existence of vestigial traits can be attributed to changes in the environment and behavior patterns of the organism in question. In some cases the structure becomes detrimental to the organism. If there are no selection pressures actively lowering the fitness of the individual, the trait will persist in future generations unless the trait is eliminated through genetic drift or other random events.
Although in many cases the vestigial structure is of no direct harm, all structures require extra energy in terms of development, maintenance, and weight and are also a risk in terms of disease e. The vestigial versions of a structure can be compared to the original version of the structure in other species in order to determine the homology of the structure. Homologous structures indicate common ancestry with those organisms that have a functional version of the structure.
Vestigial traits can still be considered adaptations because an adaptation is often defined as a trait that has been favored by natural selection. However, humans still have a coccyx or tailbone in their skeletons.
In fetuses, any tail is absorbed during development. The coccyx currently serves as an anchor for muscles; that wasn't its original purpose, so that's why it's considered vestigial. Male nipples: All people inherit nipples from both their parents, even males.
Natural selection hasn't selected against them, even though they don't have a reproductive use in males. Goosebumps: The pilomotor reflex, which raises the hair on your arms or neck when you feel alarmed, is vestigial in humans, but it's pretty useful for porcupines who raise their quills at a sign of danger—or birds, who fluff up when it gets cold.
Wisdom teeth: Our jaws have shrunk over time, so we no longer have room for wisdom teeth in our jawbone. The function of the appendix had been unknown, and it had been thought to be a useless, vestigial structure, especially because no domestic mammals have one.
However, it's now known that the appendix serves a function. Martin to Scientific American. Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads. Create a personalised ads profile.
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