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biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...
, an atavism is a modification of a biological structure whereby an ancestral genetic trait reappears after having been lost through
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
ary change in previous generations. Atavisms can occur in several ways; one of which is when
gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
s for previously existing
phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...
features are preserved in DNA, and these become expressed through a
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...
that either knocks out the dominant genes for the new traits or makes the old traits dominate the new one. A number of traits can vary as a result of shortening of the
fetal development Prenatal development () includes the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal devel ...
of a trait (
neoteny Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compa ...
) or by prolongation of the same. In such a case, a shift in the time a trait is allowed to develop before it is fixed can bring forth an ancestral phenotype. Atavisms are often seen as evidence of evolution. In
social science Social science is one of the branches of science, devoted to the study of societies and the relationships among individuals within those societies. The term was formerly used to refer to the field of sociology, the original "science of so ...
s, atavism is the tendency of reversion. For example, people in the modern era reverting to the ways of thinking and acting of a former time. The word ''atavism'' is derived from the
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
''atavus''—a great-great-great-grandfather or, more generally, an ancestor.


Biology

Evolutionarily traits that have disappeared phenotypically do not necessarily disappear from an organism's DNA. The gene sequence often remains, but is inactive. Such an unused gene may remain in the genome for many generations. As long as the gene remains intact, a fault in the genetic control suppressing the gene can lead to it being expressed again. Sometimes, the expression of dormant genes can be induced by artificial stimulation. Atavisms have been observed in humans, such as with infants born with vestigial tails (called a "coccygeal process", "coccygeal projection", or "caudal appendage"). Atavism can also be seen in humans who possess large teeth, like those of other primates. In addition, a case of "snake heart", the presence of "coronary circulation and myocardial architecture hat closelyresemble those of the reptilian heart", has also been reported in medical literature. Atavism has also recently been induced in avian
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
(
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
) fetuses to express dormant ancestral non-avian
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
(non-
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
) features, including teeth. Other examples of observed atavisms include: *Hind limbs in cetaceans and
sirenian The Sirenia (), commonly referred to as sea-cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The Sirenia currently comprise two distinct f ...
s. *Extra toes of the modern horse. *Reappearance of limbs in
limbless vertebrate Many vertebrates have evolved limbless, limb-reduced, or apodous forms. Reptiles have on a number of occasions evolved into limbless forms – snakes, amphisbaenia, and legless lizards (limb loss in lizards has evolved independently several tim ...
s. *Re-evolution of sexuality from
parthenogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and developmen ...
in oribatid mites. *Teeth in avian
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s (
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s). *
Dewclaw A dewclaw is a digit – vestigial in some animals – on the foot of many mammals, birds, and reptiles (including some extinct orders, like certain theropods). It commonly grows higher on the leg than the rest of the foot, such that in digit ...
s in
dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s. *Reappearance of
prothoracic The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on ea ...
wings in
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...
s. *Reappearance of wings on wingless stick insects and leaf insects and
earwig Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forcep-like pincers on their abdomen, and membranous wings folde ...
s. *Atavistic muscles in several
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s and mammals such as the
beagle The beagle is a breed of small scent hound, similar in appearance to the much larger foxhound. The beagle was developed primarily for hunting hare, known as beagling. Possessing a great sense of smell and superior tracking instincts, th ...
and the
jerboa Jerboas (from ar, جربوع ') are hopping desert rodents found throughout North Africa and Asia, and are members of the family Dipodidae. They tend to live in hot deserts. When chased, jerboas can run at up to . Some species are preyed on b ...
. *Extra toes in
guinea pigs The guinea pig or domestic guinea pig (''Cavia porcellus''), also known as the cavy or domestic cavy (), is a species of rodent belonging to the genus '' Cavia'' in the family Caviidae. Breeders tend to use the word ''cavy'' to describe the a ...
. *Reemergence of sexual reproduction in the
flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
'' Hieracium pilosella'' and the
Crotoniidae Crotoniidae are a family of mites of the Holosomata group that may be the first animal lineage to have abandoned sexual reproduction and then re-evolved it. This is a spectacular case of atavism, and later convergent evolution.Norton, R. (2007), ...
family of mites. *Webbed feet in adult
axolotl The axolotl (; from nci, āxōlōtl ), ''Ambystoma mexicanum'', is a paedomorphic salamander closely related to the tiger salamander. Axolotls are unusual among amphibians in that they reach adulthood without undergoing metamorphosis. I ...
s. * Human tails (not pseudo-tails) and supernumerary nipples in humans (and other primates). *
Color blindness Color blindness or color vision deficiency (CVD) is the decreased ability to see color or differences in color. It can impair tasks such as selecting ripe fruit, choosing clothing, and reading traffic lights. Color blindness may make some aca ...
in humans.


Culture

Atavism is a term in
Joseph Schumpeter Joseph Alois Schumpeter (; February 8, 1883 – January 8, 1950) was an Austrian-born political economist. He served briefly as Finance Minister of German-Austria in 1919. In 1932, he emigrated to the United States to become a professor at H ...
's explanation of
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
in twentieth-century
liberal Liberal or liberalism may refer to: Politics * a supporter of liberalism ** Liberalism by country * an adherent of a Liberal Party * Liberalism (international relations) * Sexually liberal feminism * Social liberalism Arts, entertainment and m ...
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...
. He defends the
liberal international relations theory Liberalism is a school of thought within international relations theory which revolves around three interrelated principles: * Rejection of power politics as the only possible outcome of international relations; it questions security/warfare pr ...
that an international society built on commerce will avoid war because of war's destructiveness and comparative cost. His reason for World War I is termed "atavism", in which he asserts that senescent governments in Europe (those of the German Empire,
Russian Empire The Russian Empire was an empire and the final period of the Russian monarchy from 1721 to 1917, ruling across large parts of Eurasia. It succeeded the Tsardom of Russia following the Treaty of Nystad, which ended the Great Northern War. ...
,
Ottoman Empire The Ottoman Empire, * ; is an archaic version. The definite article forms and were synonymous * and el, Оθωμανική Αυτοκρατορία, Othōmanikē Avtokratoria, label=none * info page on book at Martin Luther University) ...
, and Austro-Hungarian Empire) pulled the liberal Europe into war, and that the liberal regimes of the other continental powers did not cause it. He used this idea to say that
liberalism Liberalism is a political and moral philosophy based on the rights of the individual, liberty, consent of the governed, political equality and equality before the law."political rationalism, hostility to autocracy, cultural distaste for c ...
and commerce would continue to have a soothing effect in international relations, and that war would not arise between nations which are connected by commercial ties. This latter idea is very similar to the later Golden Arches theory.
University of London The University of London (UoL; abbreviated as Lond or more rarely Londin in post-nominals) is a federal public research university located in London, England, United Kingdom. The university was established by royal charter in 1836 as a degree ...
professor Guy Standing has identified three distinct sub-groups of the
precariat In sociology and economics, the precariat () is a neologism for a social class formed by people suffering from precarity, which means existing without predictability or security, affecting material or psychological welfare. The term is a portmant ...
, one of which he refers to as "atavists", who long for what they see as a lost past.


Social Darwinism

During the interval between the acceptance of
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
in the mid-1800s and the rise of the modern understanding of
genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...
in the early 1900s, atavism was used to account for the reappearance in an individual of a trait after several generations of absence—often called a "throw-back". The idea that atavisms could be made to accumulate by
selective breeding Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant m ...
, or breeding back, led to breeds such as the Heck cattle. This had been bred from ancient
landrace A landrace is a domesticated, locally adapted, often traditional variety of a species of animal or plant that has developed over time, through adaptation to its natural and cultural environment of agriculture and pastoralism, and due to isolatio ...
s with selected primitive traits, in an attempt of "reviving" the aurochs, an extinct species of wild
cattle Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult ma ...
. The same notions of atavisms were used by social Darwinists, who claimed that inferior races displayed atavistic traits, and represented more primitive traits than other races. Both atavism's and Ernst Haeckel's
recapitulation theory The theory of recapitulation, also called the biogenetic law or embryological parallelism—often expressed using Ernst Haeckel's phrase "ontogeny recapitulates phylogeny"—is a historical hypothesis that the development of the embryo of an a ...
are related to evolutionary progress, as development towards a greater complexity and a superior ability. In addition, the concept of atavism as part of an individualistic explanation of the causes of criminal deviance was popularised by the Italian criminologist Cesare Lombroso in the 1870s. He attempted to identify physical characteristics common to criminals and labeled those he found as atavistic, 'throw-back' traits that determined 'primitive' criminal behavior. His statistical evidence and the closely related idea of
eugenics Eugenics ( ; ) is a fringe set of beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter human gene pools by excluding people and groups judged to be inferior o ...
have long since been abandoned by the scientific community, but the concept that physical traits may affect the likelihood of criminal or unethical behavior in a person still has some scientific support.


See also

* Atavistic regression * Exaptation *
Spandrel (biology) In evolutionary biology, a spandrel is a phenotypic trait that is a byproduct of the evolution of some other characteristic, rather than a direct product of adaptive selection. Stephen Jay Gould and Richard Lewontin brought the term into biolog ...
*
Torna atrás Torna atrás () or Tornatrás is a term once used in 18th century ''Casta'' paintings to portray a mixed-race person (mestizaje, mestizo) who showed phenotypic characteristics of only one of the "original races", that is, white, black, Amerindian, ...


References


External links

*{{cite journal , last1=Bar-Maor , first1=JA , last2=Kesner , first2=KM , last3=Kaftori , first3=JK , title=Human tails , journal=The Journal of Bone and Joint Surgery. British Volume , date=November 1980 , volume=62-B , issue=4 , pages=508–510 , doi=10.1302/0301-620x.62b4.7430236 , pmid=7430236
Photograph of an additional (third) hoof of cows
Evolutionary biology Genetics