In
biology, an atavism is a modification of a biological structure whereby an ancestral genetic
trait reappears after having been lost through
evolutionary change in previous generations.[3] Atavisms can occur in several ways,[4] one of which is when
genes for previously existing
phenotypic features are preserved in
DNA, and these become expressed through a
mutation that either knocks out the dominant genes for the new traits or makes the old traits dominate the new one.[3] A number of traits can vary as a result of shortening of the
fetal development of a trait (
neoteny) 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.[5] Atavisms are often seen as
evidence of evolution.[6]
In
social sciences, 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
Latinatavus—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.[4][7] 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").[8] Atavism can also be seen in humans who possess large teeth, like those of other primates.[9] In addition, a case of "snake heart", the presence of "coronary circulation and myocardial architecture [that closely] resemble those of the reptilian heart", has also been reported in medical literature.[10] Atavism has also recently been induced in avian dinosaur (bird) fetuses to express dormant ancestral non-avian dinosaur (non-bird) features, including teeth.[11]
Atavism is a term in
Joseph Schumpeter's explanation of
World War I in twentieth-century
liberal Europe. He defends the
liberal international relations theory 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,
Ottoman Empire, 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 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.[29] This latter idea is very similar to the later
Golden Arches theory.
University of London professor
Guy Standing has identified three distinct sub-groups of the
precariat, one of which he refers to as "atavists", who long for what they see as a lost past.[30]
During the interval between the acceptance of
evolution in the mid-1800s and the rise of the modern understanding of
genetics 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".[citation needed] The idea that atavisms could be made to accumulate by
selective breeding, or
breeding back, led to breeds such as
Heck cattle.[citation needed] This had been bred from ancient
landraces with selected primitive traits, in an attempt of "reviving" the
aurochs, an
extinct species of wild cattle.[citation needed] 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.[citation needed] Both atavism's and
Ernst Haeckel's
recapitulation theory are related to
evolutionary progress, as development towards a greater complexity and a superior ability.[citation needed]
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.[31] 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 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.[32]
^Tyson R, Graham JP, Colahan PT, Berry CR (2004). "Skeletal atavism in a miniature horse". Veterinary Radiology & Ultrasound. 45 (4): 315–7.
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10.1111/j.1740-8261.2004.04060.x.
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^Simpson, G. G. (1951), Horses: The story of the horse family in the modern world and through sixty million years of evolution, Oxford University Press[page needed]
^Raynauad, A. (1977), Somites and early morphogenesis in reptile limbs. In Vertebrate Limb and Somite Morphogenesis, Cambridge University Press, London, pp. 373–386
^Matthew P. Harris; et al. (2006), "The Development of Archosaurian First-Generation Teeth in a Chicken Mutant", Current Biology, 16 (4): 371–377,
doi:10.1016/j.cub.2005.12.047,
PMID16488870
^Kukalová-Peck, Jarmila (11 March 2008). "Phylogeny of Higher Taxa in Insecta: Finding Synapomorphies in the Extant Fauna and Separating Them from Homoplasies". Evolutionary Biology. 35 (1): 4–51.
doi:
10.1007/s11692-007-9013-4.
S2CID25126171.
^
abRobert J. Raikow; et al. (1979), "The evolutionary re-establishment of a lost ancestral muscle in the bowerbird assemblage.", Condor, 81 (2): 203–206,
doi:
10.2307/1367290,
JSTOR1367290
^Robert J. Raikow (1975), "The evolutionary reappearance of ancestral muscles as developmental anomalies in two species of birds", Condor, 77 (4): 514–517,
doi:
10.2307/1366113,
JSTOR1366113
^Meyer-Rochow, Victor Benno (1989). "A report of webbed feet in a mature axolotl Siredon mexicanum and remarks on webbed feet in Urodela generally". Amphibia-Reptilia. 10: 89–92.
doi:
10.1163/156853889x00340.
Bar-Maor, JA; Kesner, KM; Kaftori, JK (November 1980). "Human tails". The Journal of Bone and Joint Surgery. British Volume. 62-B (4): 508–510.
doi:
10.1302/0301-620x.62b4.7430236.
PMID7430236.