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Sunday, November 2, 2025

Marsupial

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Marsupial
 
Marsupials
Temporal range: Paleocene–Recent Possible Late Cretaceous records

Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a relatively undeveloped state and then nurtured within a pouch on their mother's abdomen.

Extant marsupials encompass many species, including kangaroos, koalas, opossums, possums, Tasmanian devils, wombats, wallabies, and bandicoots.

Marsupials constitute a clade stemming from the last common ancestor of extant Metatheria, which encompasses all mammals more closely related to marsupials than to placentals. The evolutionary split between placentals and marsupials occurred 125–160 million years ago, in the Middle Jurassic–Early Cretaceous period.

Presently, close to 70% of the 334 extant marsupial species are concentrated on the Australian continent, including mainland Australia, Tasmania, New Guinea, and nearby islands. The remaining 30% are distributed across the Americas, primarily in South America, with thirteen species in Central America and a single species, the Virginia opossum, inhabiting North America north of Mexico.

Marsupial sizes range from a few grams in the long-tailed planigale, to several tonnes in the extinct Diprotodon.

The word marsupial comes from marsupium, the technical term for the abdominal pouch. It, in turn, is borrowed from the Latin marsupium and ultimately from the ancient Greek μάρσιππος mársippos, meaning "pouch".

Anatomy

Koala
(Phascolarctos cinereus)

Marsupials have typical mammalian characteristics—e.g., mammary glands, three middle ear bones (and ears that usually have tragi, varying in hearing thresholds), true hair and bone structure. However, striking differences including anatomical features separate them from eutherians.

Most female marsupials have a front pouch, which contains multiple nursing teats. Marsupials have other common structural features. Ossified patellae are absent in most modern marsupials (with exceptions) and epipubic bones are present. Marsupials (and monotremes) also lack a gross communication (corpus callosum) between the right and left brain hemispheres.

Skull and teeth

Marsupials exhibit distinct cranial features compared to placentals. Generally, their skulls are relatively small and compact. Notably, they possess frontal holes known as foramen lacrimale situated at the front of the orbit. Marsupials have enlarged cheekbones that extend further to the rear, and their lower jaw's angular extension (processus angularis) is bent toward the center. The hard palate of marsupials contains more openings than that of placentals.

Teeth differ significantly. Most Australian marsupials outside the order Diprotodontia have a varying number of incisors between their upper and lower jaws. Early marsupials had a dental formula of 5.1.3.4/4.1.3.4 per quadrant, consisting of five (maxillary) or four (mandibular) incisors, one canine, three premolars, and four molars, totaling 50 teeth. While some taxa, like the opossum, retain this original tooth count, others have reduced numbers.

For instance, members of the Macropodidae family, including kangaroos and wallabies, have a dental formula of 3/1 – (0 or 1)/0 – 2/2 – 4/4. Many marsupials typically have between 40 and 50 teeth, more than most placentals. In marsupials, the second set of teeth only grows in at the site of the third premolar and posteriorly; all teeth anterior to this erupt initially as permanent teeth.

Torso

Few general characteristics describe their skeleton. In addition to unique details in the construction of the ankle, epipubic bones (ossa epubica) are observed projecting forward from the pubic bone of the pelvis. Since these are present in males and pouchless species, it is believed that they originally had nothing to do with reproduction, but served in the muscular approach to the movement of the hind limbs. This could be explained by an original feature of mammals, as these epipubic bones are also found in monotremes. Marsupial reproductive organs differ from placentals. For them, the reproductive tract is doubled. Females have two uteri and two vaginas, and before birth, a birth canal forms between them, the median vagina. In most species, males have a split or double penis lying in front of the scrotum, which is not homologous to the placental scrota.

A pouch is present in most species. Many marsupials have a permanent bag, while in others such as the shrew opossum the pouch develops during gestation, where the young are hidden only by skin folds or in the maternal fur. The arrangement of the pouch is variable to allow the offspring to receive maximum protection. Locomotive kangaroos have a pouch opening at the front, while many others that walk or climb on all fours open in the back. Usually, only females have a pouch, but the male water opossum has a pouch that protects his genitalia while swimming or running.

General and convergences

The sugar glider, a marsupial, (left) and flying squirrel, a placental, (right) are examples of convergent evolution.

Marsupials have adapted to many habitats, reflected in the wide variety in their build. The largest living marsupial, the red kangaroo, grows up to 1.8 metres (5 ft 11 in) in height and 90 kilograms (200 lb) in weight. Extinct genera, such as Diprotodon, were significantly larger and heavier. The smallest marsupials are the marsupial mice, which reach only 5 centimetres (2.0 in) in body length.

Some species resemble placentals and are examples of convergent evolution. This convergence is evident in both brain evolution and behaviour. The extinct thylacine strongly resembled the placental wolf, hence one of its nicknames "Tasmanian wolf". The ability to glide evolved in both marsupials (as with sugar gliders) and some placentals (as with flying squirrels), which developed independently. Other groups such as the kangaroo, however, do not have clear placental counterparts, though they share similarities in lifestyle and ecological niches with ruminants.

Body temperature

Marsupials, along with monotremes (platypuses and echidnas), typically have lower body temperatures than similarly sized placentals (eutherians), with the averages being 35 °C (95 °F) for marsupials and 37 °C (99 °F) for placentals. Some species will bask to conserve energy.

Reproductive system

See also: Kangaroo § Reproduction and life cycle

Female eastern grey kangaroo with a joey in her pouch

Marsupials' reproductive systems differ markedly from those of placentals. During embryonic development, a choriovitelline placenta forms in all marsupials. In bandicoots, an additional chorioallantoic placenta forms, although it lacks the chorionic villi found in eutherian placentas.

Both sexes possess a cloaca, although modified by connecting to a urogenital sac and having a separate anal region in most species. The bladder of marsupials functions as a site to concentrate urine and empties into the common urogenital sinus in both females and males.

Males

Reproductive tract of a male macropod

Most male marsupials, except for macropods and marsupial moles, have a bifurcated penis, separated into two columns, so that the penis has two ends corresponding to the females' two vaginas. The penis is used only during copulation, and is separate from the urinary tract. It curves forward when erect, and when not erect, it is retracted into the body in an S-shaped curve. Neither marsupials nor monotremes possess a baculum. The shape of the glans penis varies among marsupial species.

The shape of the urethral grooves of the males' genitalia is used to distinguish between Monodelphis brevicaudata, M. domestica, and M. americana. The grooves form two channels that form the ventral and dorsal folds of the erectile tissue. Several species of dasyurid marsupials can also be distinguished by their penis morphology. Marsupials' only accessory sex glands are the prostate and bulbourethral glands. Male marsupials have one to three pairs of bulbourethral glands. Ampullae of vas deferens, seminal vesicles or coagulating glands are not present. The prostate is proportionally larger in marsupials than in placentals. During the breeding season, the male tammar wallaby's prostate and bulbourethral gland enlarge. However, the weight of the testes does not vary seasonally.

Females

See also: Birth § Marsupials
Female reproductive anatomy of several marsupial species

Female marsupials have two lateral vaginas, which lead to separate uteri, both accessed through the same orifice. A third canal, the median vagina, is used for birth. This canal can be transitory or permanent. Some marsupial species store sperm in the oviduct after mating.

Marsupials give birth very early in gestation; after birth, newborns crawl up their mothers' bodies and attach themselves to a teat, which is located on the underside of the mother, either inside a pouch called the marsupium, or externally. Mothers often lick their fur to leave a trail of scent for the newborn to follow to increase their chances of reaching the marsupium. There they remain for several weeks. Offspring eventually leave the marsupium for short periods, returning to it for warmth, protection, and nourishment.

Early development

A red-necked wallaby joey inside its mother's pouch

Gestation differs between marsupials and placentals. Key aspects of the first stages of placental embryo development, such as the inner cell mass and the process of compaction, are not found in marsupials. The cleavage stages of marsupial development vary among groups and aspects of marsupial early development are not yet fully understood.

Marsupials have a short gestation period—typically between 12 and 33 days, but as low as 10 days in the case of the stripe-faced dunnart and as long as 38 days for the long-nosed potoroo. The baby (joey) is born in a fetal state, equivalent to an 8–12 week human fetus, blind, furless, and small in comparison to placental newborns: sizes range from 4-800g+. A newborn can be categorized in one of three grades of development. The least developed are found in dasyurids, intermediates are found in didelphids and peramelids, and the most developed are macropods. The newborn crawls across its mother's fur to reach the pouch, where it latches onto a teat. It does not emerge for several months, during which time it relies on its mother's milk for essential nutrients, growth factors and immunological defence. Genes expressed in the eutherian placenta needed for the later stages of fetal development are expressed in females in their mammary glands during lactation. After this period, the joey spends increasing periods out of the pouch, feeding and learning survival skills. However, it returns to the pouch to sleep, and if danger threatens, it seeks refuge in its mother's pouch.

An early birth removes a developing marsupial from its mother's body much sooner than in placentals; thus marsupials lack a complex placenta to protect the embryo from its mother's immune system. Though early birth puts the newborn at greater environmental risk, it significantly reduces the dangers associated with long pregnancies, as the fetus cannot compromise the mother in bad seasons. Marsupials are altricial animals, needing intensive care following birth (cf. precocial). Newborns lack histologically mature immune tissues and are highly reliant on their mother's immune system for immunological protection.

Newborns front limbs and facial structures are much more developed than the rest of their bodies at birth. This requirement has been argued to have limited the range of locomotor adaptations in marsupials compared to placentals. Marsupials must develop grasping forepaws early, complicating the evolutive transition from these limbs into hooves, wings, or flippers. However, several marsupials do possess atypical forelimb morphologies, such as the hooved forelimbs of the pig-footed bandicoot, suggesting that the range of forelimb specialization is not as limited as assumed.

Joeys stay in the pouch for up to a year or until the next joey arrives. Joeys are unable to regulate their body temperature and rely upon an external heat source. Until the joey is well-furred and old enough to leave the pouch, a pouch temperature of 30–32 °C (86–90 °F) must be constantly maintained.

Joeys are born with "oral shields", soft tissue that reduces the mouth opening to a round hole just large enough to accept the teat. Once inside the mouth, a bulbous swelling on the end of the teat attaches it to the offspring till it has grown large enough to let go. In species without pouches or with rudimentary pouches these are more developed than in forms with well-developed pouches, implying an increased role in ensuring that the young remain attached to the teat.

Range

In Australasia, marsupials are found in Australia, Tasmania and New Guinea; throughout the Maluku Islands, Timor and Sulawesi to the west of New Guinea, and in the Bismarck Archipelago (including the Admiralty Islands) and Solomon Islands to the east of New Guinea.

In the Americas, marsupials are found throughout South America, excluding the central/southern Andes and parts of Patagonia; and through Central America and south-central Mexico, with a single species (the Virginia opossum Didelphis virginiana) widespread in the eastern United States and along the Pacific coast.

Interaction with Europeans

Europeans' first encounter with a marsupial was the common opossum. Vicente Yáñez Pinzón, commander of the Niña on Christopher Columbus' first voyage in the late fifteenth century, collected a female opossum with young in her pouch off the South American coast. He presented them to the Spanish monarchs, though by then the young were lost and the female had died. The animal was noted for its strange pouch or "second belly".

The Portuguese first described Australasian marsupials: António Galvão, a Portuguese administrator in Ternate (1536–1540), wrote a detailed account of the northern common cuscus (Phalanger orientalis):

Some animals resemble ferrets, only a little bigger. They are called Kusus. They have a long tail with which they hang from the trees in which they live continuously, winding it once or twice around a branch. On their belly they have a pocket like an intermediate balcony; as soon as they give birth to a young one, they grow it inside there at a teat until it does not need nursing anymore. As soon as she has borne and nourished it, the mother becomes pregnant again.

In the 17th century, more accounts of marsupials emerged. A 1606 record of an animal killed on the southern coast of New Guinea, described it as "in the shape of a dog, smaller than a greyhound", with a snakelike "bare scaly tail" and hanging testicles. The meat tasted like venison, and the stomach contained ginger leaves. This description appears to closely resemble the dusky pademelon (Thylogale brunii), the earliest European record of a member of the Macropodidae.

Taxonomy

Marsupials are taxonomically identified as members of mammalian infraclass Marsupialia, first described as a family under the order Pollicata by German zoologist Johann Karl Wilhelm Illiger in his 1811 work Prodromus Systematis Mammalium et Avium. However, James Rennie, author of The Natural History of Monkeys, Opossums and Lemurs (1838), pointed out that the placement of five different groups of mammals – monkeys, lemurs, tarsiers, aye-ayes and marsupials (with the exception of kangaroos, which were placed under the order Salientia) – under a single order (Pollicata) did not appear to have a strong justification. In 1816, French zoologist George Cuvier classified all marsupials under Marsupialia. In 1997, researcher J. A. W. Kirsch and others accorded infraclass rank to Marsupialia.

Classification

With seven living orders in total, Marsupialia is further divided as follows:† – Extinct

Evolutionary history

See also: Metatheria, Evolution of Macropodidae, and Evolution of mammals

Comprising over 300 extant species, several attempts have been made to accurately interpret the phylogenetic relationships among the different marsupial orders. Studies differ on whether Didelphimorphia or Paucituberculata is the sister group to all other marsupials. Though the order Microbiotheria (which has only one species, the monito del monte) is found in South America, morphological similarities suggest it is closely related to Australian marsupials. Molecular analyses in 2010 and 2011 identified Microbiotheria as the sister group to all Australian marsupials. However, the relations among the four Australidelphid orders are not as well understood.

Isolated petrosals of Djarthia murgonensis, Australia's oldest marsupial fossils
Dentition of the herbivorous eastern grey kangaroo, as illustrated in Knight's Sketches in Natural History
Phylogenetic tree of marsupials derived from retroposon data

DNA evidence supports a South American origin for marsupials, with Australian marsupials arising from a single Gondwanan migration of marsupials from South America, across the Antarctic land bridge, to Australia. There are many small arboreal species in each group. The term "opossum" is used to refer to American species (though "possum" is a common abbreviation), while similar Australian species are properly called "possums".

The relationships among the three extant divisions of mammals (monotremes, marsupials, and placentals) were long a matter of debate among taxonomists. Most morphological evidence comparing traits such as number and arrangement of teeth and structure of the reproductive and waste elimination systems as well as most genetic and molecular evidence favors a closer evolutionary relationship between the marsupials and placentals than either has with the monotremes.

The ancestors of marsupials, part of a larger group called metatherians, probably split from those of placentals (eutherians) during the mid-Jurassic period, though no fossil evidence of metatherians themselves are known from this time. From DNA and protein analyses, the time of divergence of the two lineages has been estimated to be around 100 to 120 mya. Fossil metatherians are distinguished from eutherians by the form of their teeth; metatherians possess four pairs of molar teeth in each jaw, whereas eutherian mammals (including true placentals) never have more than three pairs. Using this criterion, the earliest known metatherian was thought to be Sinodelphys szalayi, which lived in China around 125 mya. However Sinodelphys was later reinterpreted as an early member of Eutheria. The unequivocal oldest known metatherians are now 110 million years old fossils from western North America. Metatherians were widespread in North America and Asia during the Late Cretaceous, but suffered a severe decline during the end-Cretaceous extinction event.

Metatheria

In 2022, a study provided strong evidence that the earliest known marsupial was Deltatheridium known from specimens from the Campanian age of the Late Cretaceous in Mongolia. This study placed both Deltatheridium and Pucadelphys as sister taxa to the modern large American opossums.

Marsupials spread to South America from North America during the Paleocene, possibly via the Aves Ridge. Northern Hemisphere metatherians, which were of low morphological and species diversity compared to contemporary placental mammals, eventually became extinct during the Miocene epoch.

In South America, the opossums evolved and developed a strong presence, and the Paleogene also saw the evolution of shrew opossums (Paucituberculata) alongside non-marsupial metatherian predators such as the borhyaenids and the saber-toothed Thylacosmilus. South American niches for mammalian carnivores were dominated by these marsupial and sparassodont metatherians, which seem to have competitively excluded South American placentals from evolving carnivory. While placental predators were absent, the metatherians did have to contend with avian (terror bird) and terrestrial crocodylomorph competition. Marsupials were excluded in turn from large herbivore niches in South America by the presence of native placental ungulates (now extinct) and xenarthrans (whose largest forms are also extinct). South America and Antarctica remained connected until 35 mya, as shown by the unique fossils found there. North and South America were disconnected until about three million years ago, when the Isthmus of Panama formed. This led to the Great American Interchange. Sparassodonts disappeared for unclear reasons – again, this has classically assumed as competition from carnivoran placentals, but the last sparassodonts co-existed with a few small carnivorans like procyonids and canines, and disappeared long before the arrival of macropredatory forms like felines, while didelphimorphs (opossums) invaded Central America, with the Virginia opossum reaching as far north as Canada.

Marsupials reached Australia via the Antarctic Land Bridge during the Early Eocene, around 50 mya, shortly after Australia had split off. This suggests a single dispersion event of just one species, most likely a relative to South America's monito del monte (a microbiothere, the only New World australidelphian). This progenitor may have rafted across the widening, but still narrow, gap between Australia and Antarctica. The journey must not have been easy; South American ungulate and xenarthran remains have been found in Antarctica, but these groups did not reach Australia.

In Australia, marsupials radiated into the wide variety seen today, including not only omnivorous and carnivorous forms such as were present in South America, but also into large herbivores. Modern marsupials appear to have reached the islands of New Guinea and Sulawesi relatively recently via Australia. A 2010 analysis of retroposon insertion sites in the nuclear DNA of a variety of marsupials has confirmed all living marsupials have South American ancestors. The branching sequence of marsupial orders indicated by the study puts Didelphimorphia in the most basal position, followed by Paucituberculata, then Microbiotheria, and ending with the radiation of Australian marsupials. This indicates that Australidelphia arose in South America, and reached Australia after Microbiotheria split off.

In Australia, terrestrial placentals disappeared early in the Cenozoic (their most recent known fossils being 55 million-year-old teeth resembling those of condylarths) for reasons that are not clear, allowing marsupials to dominate the Australian ecosystem. Extant native Australian terrestrial placentals (such as hopping mice) are relatively recent immigrants, arriving via island hopping from Southeast Asia.

Genetic analysis suggests a divergence date between the marsupials and the placentals at 160 million years ago. The ancestral number of chromosomes has been estimated to be 2n = 14.

A recent hypothesis suggests that South American microbiotheres resulted from a back-dispersal from eastern Gondwana. This interpretation is based on new cranial and post-cranial marsupial fossils of Djarthia murgonensis from the early Eocene Tingamarra Local Fauna in Australia that indicate this species is the most plesiomorphic ancestor, the oldest unequivocal australidelphian, and may be the ancestral morphotype of the Australian marsupial radiation.

In 2023, imaging of a partial skeleton found in Australia by paleontologists from Flinders University led to the identification of Ambulator keanei, the first long-distance walker in Australia.

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Saturday, November 1, 2025

Taxon

From Wikipedia, the free encyclopedia
African elephants form the genus Loxodonta, a widely accepted taxon.

In biology, the taxon (back-formation from taxonomy; pl.: taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking, especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion, especially in the context of rank-based ("Linnaean") nomenclature (much less so under phylogenetic nomenclature). If a taxon is given a formal scientific name, its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping.

Initial attempts at classifying and ordering organisms (plants and animals) were presumably set forth in prehistoric times by hunter-gatherers, as suggested by the fairly sophisticated folk taxonomies. Much later, Aristotle, and later still, European scientists, like Magnol, Tournefort and Carl Linnaeus's system in Systema Naturae, 10th edition (1758),, as well as an unpublished work by Bernard and Antoine Laurent de Jussieu, contributed to this field. The idea of a unit-based system of biological classification was first made widely available in 1805 in the introduction of Jean-Baptiste Lamarck's Flore françoise, and Augustin Pyramus de Candolle's Principes élémentaires de botanique. Lamarck set out a system for the "natural classification" of plants. Since then, systematists continue to construct accurate classifications encompassing the diversity of life; today, a "good" or "useful" taxon is commonly taken to be one that reflects evolutionary relationships.

Many modern systematists, such as advocates of phylogenetic nomenclature, use cladistic methods that require taxa to be monophyletic (all descendants of some ancestor). Therefore, their basic unit, the clade, is equivalent to the taxon, assuming that taxa should reflect evolutionary relationships. Similarly, among those contemporary taxonomists working with the traditional Linnean (binomial) nomenclature, few propose taxa they know to be paraphyletic. An example of a long-established taxon that is not also a clade is the class Reptilia, the reptiles; birds and mammals are the descendants of animals traditionally classed as reptiles, but neither is included in the Reptilia (birds are traditionally placed in the class Aves, and mammals in the class Mammalia).

History

The term taxon was first used in 1926 by Adolf Meyer-Abich for animal groups, as a back-formation from the word taxonomy; the word taxonomy had been coined a century before from the Greek components τάξις (táxis), meaning "arrangement", and νόμος (nómos), meaning "method". For plants, it was proposed by Herman Johannes Lam in 1948, and it was adopted at the VII International Botanical Congress, held in 1950.

Definition

The glossary of the International Code of Zoological Nomenclature (1999) defines a

  • "taxon, (pl. taxa), n.
A taxonomic unit, whether named or not: i.e. a population, or group of populations of organisms which are usually inferred to be phylogenetically related and which have characters in common which differentiate (q.v.) the unit (e.g. a geographic population, a genus, a family, an order) from other such units. A taxon encompasses all included taxa of lower rank (q.v.) and individual organisms. [...]"

Ranks

LifeDomainKingdomPhylumClassOrderFamilyGenusSpecies
The hierarchy of biological classification's eight major taxonomic ranks. Intermediate minor rankings are not shown.

A taxon can be assigned a taxonomic rank, usually (but not necessarily) when it is given a formal name.

"Phylum" applies formally to any biological domain, but traditionally it was always used for animals, whereas "division" was traditionally often used for plants, fungi, etc.

A prefix is used to indicate a ranking of lesser importance. The prefix super- indicates a rank above, the prefix sub- indicates a rank below. In zoology, the prefix infra- indicates a rank below sub-. For instance, among the additional ranks of class are superclass, subclass and infraclass.

Rank is relative, and restricted to a particular systematic schema. For example, liverworts have been grouped, in various systems of classification, as a family, order, class, or division (phylum). The use of a narrow set of ranks is challenged by users of cladistics; for example, the mere 10 ranks traditionally used between animal families (governed by the International Code of Zoological Nomenclature (ICZN)) and animal phyla (usually the highest relevant rank in taxonomic work) often cannot adequately represent the evolutionary history as more about a lineage's phylogeny becomes known.

In addition, the class rank is quite often not an evolutionary but a phenetic or paraphyletic group and as opposed to those ranks governed by the ICZN (family-level, genus-level and species-level taxa), can usually not be made monophyletic by exchanging the taxa contained therein. This has given rise to phylogenetic taxonomy and the ongoing development of the PhyloCode, which has been proposed as a new alternative to replace Linnean classification and govern the application of names to clades. Many cladists do not see any need to depart from traditional nomenclature as governed by the ICZN, International Code of Nomenclature for algae, fungi, and plants, etc.

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Minority group

From Wikipedia, the free encyclopedia

The term "minority group" has different meanings, depending on the context. According to common usage, it can be defined simply as a group in society with the lowest number of individuals, or less than half of a population. Usually a minority group is disempowered relative to the majority, and that characteristic lends itself to different applications of the term minority.

In terms of sociology, economics, and politics, a demographic that takes up the smallest fraction of the population is not necessarily labelled the "minority" if it wields dominant power. In the academic context, the terms "minority" and "majority" are used in terms of hierarchical power structures. For example, in South Africa, during Apartheid, white Europeans held virtually all social, economic, and political power over black Africans. For this reason, black Africans are the "minority group", despite the fact that they outnumber white Europeans in South Africa. This is why academics more frequently use the term "minority group" to refer to a category of people who experience relative disadvantage, as compared to members of a dominant social group. To address this ambiguity, Harris Mylonas has proposed the term "non-core group", instead of "minority group", to refer to any aggregation of individuals that is perceived as an unassimilated ethnic group (on a linguistic, religious, physical, or ideological basis) by the ruling political elite of a country" and reserves the term 'minority' only for groups that have been granted minority rights by their state of residence.

Minority group membership is typically based on differences in observable characteristics or practices, such as: ethnicity (ethnic minority), race (racial minority), religion (religious minority), sexual orientation (sexual minority), or disability. The framework of intersectionality can be used to recognize that an individual may simultaneously hold membership in multiple minority groups (e.g. both a racial and religious minority). Likewise, individuals may also be part of a minority group in regard to some characteristics, but part of a dominant group in regard to others.

The term "minority group" often occurs within the discourse of civil rights and collective rights, as members of minority groups are prone to differential treatment in the countries and societies in which they live. Minority group members often face discrimination in multiple areas of social life, including housing, employment, healthcare, and education, among others. While discrimination may be committed by individuals, it may also occur through structural inequalities, in which rights and opportunities are not equally accessible to all. Those in favour of minority rights often pursue laws designed to protect minority groups from discrimination and afford members of the minority group equal social status and legal protections as held by members of the dominant group.

Definitions

In the 19th century, the term "minority" primarily referred to political parties in national legislatures. The term minority referred to a range of groups, including the better-educated and better-off who were worried of being swamped by broadening franchise (voting rights). As Jenifer Hart put it, "those who have" felt threatened by "those who want"; the less-popular party in a two-party contest, who should not have control or power but in many electoral systems is able to do so; and a least-popular "third party" as workers, farmers and socialists enter into electoral politics and receive substantial support, and thereby should have representation but in many electoral systems do not.

This changed with the Paris Peace Conference (1919–1920), when the term "minority" was applied to ethnic, national, linguistic and religious groups who made up less than half of the population of a state, "groups of persons who differ in race, religion or language from the majority of the inhabitants of the country." The Paris Conference has been attributed with coining the concept of minority rights and bringing prominence to it. The League of Nations Minorities Commission in 1919 defined members of a minority as "nationals belonging to racial, religious, or linguistic minorities". Protection of minority groups, such as through careful drawing of boundaries of states and proportional representation, was seen as integral in preventing causes of future wars.

Sociological

Louis Wirth defined a minority group as "a group of people who, because of their physical or cultural characteristics, are singled out from the others in the society in which they live for differential and unequal treatment, and who therefore regard themselves as objects of collective discrimination". The definition includes both objective and subjective criteria: membership of a minority group is objectively ascribed by society, based on an individual's physical or behavioral characteristics; it is also subjectively applied by its members, who may use their status as the basis of group identity or solidarity. Thus, minority group status is categorical: an individual who exhibits the physical or behavioral characteristics of a given minority group is accorded the status of that group and is subject to the same treatment as other members of that group.

Joe Feagin, states that a minority group has five characteristics: (1) suffering discrimination and subordination, (2) physical and/or cultural traits that set them apart, and which are disapproved by the dominant group, (3) a shared sense of collective identity and common burdens, (4) socially shared rules about who belongs and who does not determine minority status, and (5) tendency to marry within the group.

Criticisms

There is a controversy with the use of the word minority, as it has a generic and an academic usage. Common usage of the term indicates a statistical minority; however, academics refer to power differences among groups rather than differences in population size among groups.

Such use of the term minority is based on the idea that a group can be considered a minority even if it includes such a large number of people that it is numerically not a minority in society.

Some sociologists have criticized the concept of "minority/majority", arguing this language excludes or neglects changing or unstable cultural identities, as well as cultural affiliations across national boundaries. As such, the term historically excluded groups (HEGs) is often similarly used to highlight the role of historical oppression and domination, and how this results in the under-representation of particular groups in various areas of social life.

Political

The term national minority is often used to discuss minority groups in international and national politics. All countries contain some degree of racial, ethnic, or linguistic diversity. In addition, minorities may also be immigrant, indigenous or landless nomadic communities. This often results in variations in language, culture, beliefs, practices, that set some groups apart from the dominant group. As these differences are usually perceived negatively, this results in loss of social and political power for members of minority groups.

There is no legal definition of national minorities in international law, though protection of minority groups is outlined by the United Nations Declaration on the Rights of Persons Belonging to National or Ethnic, Religious and Linguistic Minorities. International criminal law can protect the rights of racial or ethnic minorities in several ways. The right to self-determination is a key issue. The Council of Europe regulates minority rights in the European Charter for Regional or Minority Languages and the Framework Convention for the Protection of National Minorities.

In some places, subordinate ethnic groups may constitute a numerical majority, such as Blacks in South Africa under apartheid. In the United States, for example, non-Hispanic Whites constitute the majority (58.4%) and all other racial and ethnic groups (Central and South Americans, African Americans, Asian Americans, American Indian, and Native Hawaiians) are classified as "minorities". If the non-Hispanic White population falls below 50% the group will only be the plurality, not the majority.

Examples

Racial and ethnic minorities

Racial minorities, sometimes referred to synonymously as people of color or non-white people, are minority groups that are discriminated against on the basis of race. Though definitions vary cross-culturally, modern racism is primarily based on the European and American classifications of race that developed during the Age of Exploration, as European countries sought to categorize the nations they colonized into pseudo-scientific phenotypical groups. In the United States's system, whiteness is at the top of a hierarchy that automatically classifies mixed-race individuals as their subordinate race.

Sometimes, racist policies explicitly codified pseudo-scientific definitions of race: such as the United States' one-drop rule and blood quantum laws, South Africa's apartheid, and Nazi Germany Nuremberg race laws. Other times, race has been a matter of self-identification, with de facto racist policies implemented. In addition to governmental policy, racism may persist as social prejudice and discrimination.

There are also social groups that are usually identified through ethnicity. Like race, ethnicity is largely determined hereditarily. However, it can also be influenced by factors such as adoption, cultural assimilation, religious conversion, and language shift. As race and ethnicity often overlap, many ethnic minorities are also racial minorities. However, this is not always the case, and some people are ethnic minorities while also being classified as white, such as some Jews, Roma, and Sámi. In some cases, their ethnic identities have been seen as negating their whiteness, in both inter- and intra-group identification.

In some countries, such as the United Kingdom, there is a preference to categorise people by ethnicity instead of race. Ethnicity encompasses a mix of "long shared cultural experiences, religious practices, traditions, ancestry, language, dialect or national origins". The United Kingdom considers everyone but white British people to be an ethnic minority, including other white Europeans such as White Irish people (excluding in Northern Ireland).

National minorities

A national minority is a social group within a state that differs from the majority and/or dominant population in terms of ethnicity, language, culture, or religion, but also it also tends to have a close link with a specific territory from which the minority social group originates.

Involuntary minorities

Also known as "castelike minorities", involuntary minorities are a term for people who were originally brought into any society against their will. In the United States, for instance, it includes but is not limited to Native Americans, Native Hawaiians, Puerto Ricans, African Americans, and in the 1800s, native-born Hispanics.

Voluntary minorities

Immigrants take on minority status in their new country, usually in hopes of a better future economically, educationally, and politically than in their homeland. Because of their focus on success, voluntary minorities are more likely to do better in school than other migrating minorities. Adapting to a very different culture and language makes difficulties in the early stages of life in the new country. Voluntary immigrants do not experience a sense of divided identity as much as involuntary minorities and are often rich in social capital because of their educational ambitions. Major immigrant groups in the United States include Mexicans, Central and South Americans, Cubans, Africans, East Asians, and South Asians.

Gender and sexuality minorities

Main article: Sexual minority
Pride events are held annually around the world for sexual minorities. In picture, people gathering at the Senate Square, Helsinki, right before the 2011 Helsinki Pride parade started.

The term sexual minority is frequently used by public health researchers to recognize a wide variety of individuals who engage in same-sex sexual behavior, including those who do not identify under the LGBTQ+ umbrella. For example, men who have sex with men (MSM), but do not identify as gay. In addition, the term gender minorities can include many types of gender variant people, such as intersex people, transgender people, or non-binary individuals. However, the terms sexual and gender minority are often not preferred by LGBTQ+ people, as they represent clinical categories rather than individual identity.

Though lesbian, gay, bisexual, transgender, and queer (LGBTQ+) people have existed throughout human history, they represent a numerical and social minority. They experience numerous social inequalities stemming from their group membership as LGBTQ+ people. LGBTQ+ rights movements across many western countries led to the recognition of LGBTQ+ people as members of a minority group. These inequalities include social discrimination and isolation, unequal access to healthcare, employment, and housing, and experience negative mental and physical health outcomes due to these experiences.

Disabled people

Leading up to the Human Rights Act 1998 in the UK, a rise in the awareness relating to how disabled people were being treated began. Many started to believe that they were being denied basic human rights. This act had a section that stated if authorities did not protect people with learning disabilities from others' actions, such as harm or neglect, then they could be prosecuted.

The disability rights movement has contributed to an understanding of disabled people as a minority or a coalition of minorities who are disadvantaged by society, not just as people who are disadvantaged by their impairments. Advocates of disability rights emphasize the difference in physical or psychological functioning rather than inferiority. For example, some autistic people argue for acceptance of neurodiversity, much as opponents of racism argue for acceptance of ethnic diversity. The deaf community is often regarded as a linguistic and cultural minority rather than a group with disabilities, and some deaf people do not see themselves as having a disability at all. Rather, they are disadvantaged by technologies and social institutions designed to cater to the dominant group. (See the Convention on the Rights of Persons with Disabilities.)

Religious minorities

Main article: Minority religion

People belonging to religious minorities have a faith that is different from that held by the majority. Most countries of the world have religious minorities. It is now widely accepted in the West that people should have the freedom to choose their religion, including the right to convert from one religion to another, or not to have any religion (atheism and/or agnosticism). However, in many countries, this freedom is constricted. In Egypt, a new system of identity cards requires all citizens to state their religion—and the only choices are Islam, Christianity, or Judaism (See Egyptian identification card controversy).

Women as a disadvantaged group

In most societies, numbers of men and women are roughly equal. Though women are not considered to be a minority, the status of women, as a subordinate group, has led to many social scientists to refer to them as a disadvantaged group. Though women's legal rights and status vary widely across countries, women often experience social inequalities, relative to men, in various societies. Women are sometimes denied access to education and access to the same opportunities as men, especially in under-developed countries.

Law and government

In the politics of some countries, a "minority" is an ethnic group recognized by law, and having specified rights. Speakers of a legally recognized minority language, for instance, might have the right to education or communication with the government in their mother tongue. Countries with special provisions for minorities include Canada, China, Ethiopia, Germany, India, the Netherlands, Poland, Romania, Russia, Croatia, and the United Kingdom.

The various minority groups in a country are often not given equal treatment. Some groups are too small or indistinct to obtain minority protections. For example, a member of a particularly small ethnic group might be forced to check "Other" on a checklist of different backgrounds and so might receive fewer privileges than a member of a more defined group.

Many contemporary governments prefer to assume the people they rule all belong to the same nationality rather than separate ones based on ethnicity. The United States asks for race and ethnicity on its official census forms, which thus breaks up and organizes its population into sub-groups, primarily racial rather than national. Spain does not divide its nationals by ethnic group or national minorities, although it does maintain an official notion of minority languages, that is one of the criteria for to determine a national minority, upon the Framework Convention for the Protection of National Minorities.

Some especially significant or powerful minorities receive comprehensive protection and political representation. For example, the former Yugoslav Republic of Bosnia and Herzegovina recognizes the three constitutive nations, none of which constitutes a numerical majority (see nations of Bosnia and Herzegovina). However, other minorities such as Roma and Jews, are officially labelled "foreign" and are excluded from many of these protections. For example, they may be excluded from political positions, including the presidency.

There is debate over recognizing minority groups and their privileges. One view is that the application of special rights to minority groups may harm some countries, such as new states in Africa or Latin America not founded on the European nation-state model, since minority recognition may interfere with establishing a national identity. It may hamper the integration of the minority into mainstream society, perhaps leading to separatism or supremacism. In Canada, some feel that the failure of the dominant English-speaking majority to integrate French Canadians has provoked Quebec separatism.

Others assert that minorities require specific protections to ensure that they are not marginalized: for example, bilingual education may be needed to allow linguistic minorities to fully integrate into the school system and compete equally in society. In this view, rights for minorities strengthen the nation-building project, as members of minorities see their interests well served, and willingly accept the legitimacy of the nation and their integration (not assimilation) within it.

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