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Early embryos of various species display some ancestral features, like the tail on this human embryo. These features normally disappear in later development, but it may not happen if the animal has an atavism.[1][2]

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 Latin atavus—a great-great-great-grandfather or, more generally, an ancestor.



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]

Other examples of observed atavisms include:



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]

Social Darwinism


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]

See also



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  2. ^ "Multi-cell Organisms". Universe-review.ca. Retrieved 2011-09-29.
  3. ^ a b c d e f g h i Brian K. Hall (1984), "Developmental mechanisms underlying the atavisms", Biological Reviews, 59 (1): 89–124, doi:10.1111/j.1469-185x.1984.tb00402.x, PMID 6367843, S2CID 29258934
  4. ^ a b c Tomic, Nenad; Meyer-Rochow, Victor Benno (2011). "Atavisms - medical, genetic, and evolutionary implications". Perspectives in Biology and Medicine. 54 (3): 332–353. doi:10.1353/pbm.2011.0034. PMID 21857125. S2CID 40851098.
  5. ^ Held, L. (2009). Quirks of Human Anatomy, an Evo-Devo Look at the Human Body. Cambridge University Press. ISBN 978-0-521-73233-8.
  6. ^ a b Brian K. Hall (1995), "Atavisms and atavistic mutations", Nature Genetics, 10 (2): 126–127, doi:10.1038/ng0695-126, PMID 7663504, S2CID 27868367
  7. ^ Collin, R.; Cipriani, R. (2003). "Dollo's law and the re-evolution of shell coiling". Proceedings of the Royal Society B. 270 (1533): 2551–2555. doi:10.1098/rspb.2003.2517. PMC 1691546. PMID 14728776.
  8. ^ "29+ Evidences for Macroevolution: Part 2". Archived from the original on 29 October 2006. Retrieved 2006-11-08.
  9. ^ "What our tails tell us". Los Angeles Times. 2007-02-15. Archived from the original on 12 March 2009. Retrieved 2009-03-08.
  10. ^ Walia, I.; Arora, H. S.; Barker, E. A.; Delgado R.M., III; Frazier, O. H. (2010). "Snake Heart: A Case of Atavism in a Human Being". Texas Heart Institute Journal. 37 (6): 687–690. PMC 3014134. PMID 21224948.
  11. ^ "Dino-Chicken Gets One Step Closer". Live Science. 19 May 2015.
  12. ^ Hiroko Tabuchi (November 5, 2006), Dolphin May Have 'Remains' of Legs, Livescience.com
  13. ^ Tyson R, Graham JP, Colahan PT, Berry CR (2004). "Skeletal atavism in a miniature horse". Veterinary Radiology & Ultrasound. 45 (4): 315–7. doi:10.1111/j.1740-8261.2004.04060.x. PMID 15373256.
  14. ^ 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]
  15. ^ Raynauad, A. (1977), Somites and early morphogenesis in reptile limbs. In Vertebrate Limb and Somite Morphogenesis, Cambridge University Press, London, pp. 373–386
  16. ^ Katja Domes; et al. (2007), "Reevolution of sexuality breaks Dollo's law", Proc. Natl. Acad. Sci. U.S.A., 104 (17): 7139–7144, Bibcode:2007PNAS..104.7139D, doi:10.1073/pnas.0700034104, PMC 1855408, PMID 17438282
  17. ^ 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, PMID 16488870
  18. ^ Elias-Neto, Moysés; Belles, Xavier (3 August 2016). "Tergal and pleural structures contribute to the formation of ectopic prothoracic wings in cockroaches". Royal Society Open Science. 3 (8): 160347. Bibcode:2016RSOS....360347E. doi:10.1098/rsos.160347. PMC 5108966. PMID 27853616.
  19. ^ 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. S2CID 25126171.
  20. ^ Michael F. Whiting; et al. (2003), "Loss and recovery of wings in stick insects", Nature, 421 (6920): 264–267, Bibcode:2003Natur.421..264W, doi:10.1038/nature01313, PMID 12529642, S2CID 962571
  21. ^ a b Robert 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, JSTOR 1367290
  22. ^ 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, JSTOR 1366113
  23. ^ E. Evansh (1959), "Hyoid muscle anomalies in the dog (Canis familiaris)", Anatomical Record, 133 (2): 145–162, doi:10.1002/ar.1091330204, PMID 13670435, S2CID 33397424
  24. ^ William E. Castle (1906), The origin of a polydactylous race of guinea-pigs (49 ed.), Carnegie Institution of Washington
  25. ^ Domes, K.; Norton, R. A.; Maraun, M.; Scheu, S. (2007). "Reevolution of sexuality breaks Dollo's law". Proceedings of the National Academy of Sciences. 104 (17): 7139–7144. Bibcode:2007PNAS..104.7139D. doi:10.1073/pnas.0700034104. PMC 1855408. PMID 17438282.
  26. ^ 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.
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  29. ^ Joseph Schumpeter (1969). "Imperialism and Capitalism". Imperialism and Social Classes. Cleveland: The World Publishing Company.
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