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.[
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In biology, an atavism is a modification of a biological traits structure or behavior[ 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.]
Atavisms are often seen as evidence of evolution.
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In , 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.
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.
Atavisms have been observed in humans, such as with infants born with (called a "coccygeal process", "coccygeal projection", or "caudal appendage").
Other examples of observed atavisms include:
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Hind limbs in and .
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Extra toes of the modern horse.
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Reappearance of limbs in limbless vertebrates.
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Re-evolution of sexuality from parthenogenesis in Oribatida.
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Teeth in avian ().
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in dogs.
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Reappearance of Prothorax wings in .
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Reappearance of wings on wingless Phasmatodea
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Atavistic muscles in several
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Extra toes in guinea pigs.
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Reemergence of sexual reproduction in the flowering plant Hieracium pilosella and the Crotoniidae family of mites.
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Webbed feet in adult .
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Human tails (not pseudo-tails)
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Color blindness in humans.
Culture
Atavism is a term in Joseph Schumpeter's explanation of World War I in twentieth-century Liberalism 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.
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.
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". The idea that atavisms could be made to accumulate by selective breeding, or breeding back, led to breeds such as Heck cattle. This had been bred from ancient with selected primitive traits, in an attempt of "reviving" the aurochs, an extinct species of wild cattle. The same notions of atavisms were used by social Darwinism, 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 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.
See also
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