atavism

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

Atavism is the tendency to revert to ancestral type. In biology, an atavism is an evolutionary throwback, such as traits reappearing which had disappeared generations before.^[2] Atavisms can occur in several ways. One way is when genes for previously existing phenotypical features are preserved in DNA, and these become expressed through a mutation that either knock out the overriding genes for the new traits or make the old traits override the new one. 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.^[3]

In the social sciences, atavism is a cultural tendency—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. An atavus is a great-great-great-grandfather or, more generally, an ancestor.

Examples

Evolutionarily, traits that have disappeared phenotypically do not necessarily disappear from an organism's DNA. The gene sequence often remains, but is inactive. Mathematically, such an unused gene has a reasonable probability of remaining in the genome in a functional state for around 6 million years, but after 10 million years it is almost certain that the gene will no longer function.^[4] As long as the gene remains intact, a fault in the genetic control suppressing the gene can lead to it being expressed again. Sometimes, dormant genes can be induced to be expressed by supplying the stimuli artificially.

Examples observed include:

• Hind legs on whales^[2] or snakes
• Hind fins on dolphins^[2]
• Extra toes on horses, as in archaic horses^[5]
• Re-emergence of sexual reproduction in Hieracium pilosella and Crotoniidae^[6]
• Teeth in chickens^[7]

Examples in humans

Atavisms have been observed in humans as well. Babies have been born with a vestigial tail, called "coccygeal process", "coccygeal projection", and "caudal appendage".^[2] It can also be evidenced in humans who possess large teeth, like those of other primates.^[8] In addition a case of "Snake Heart" has also been reported in medical literature.^[9]

• Humans with extra nipples (Accessory breast)^[1]
• Humans with large canine teeth^[1]

Atavism in history

During the interval between the acceptance of evolution and the rise of modern understanding of genetics, atavism was used to account for the reappearance in an individual of a trait after several generations of absence. Such an individual was sometimes called a "throwback". The term is often used in connection with the unexpected reappearance of primitive traits in organisms.

The notion of atavism was used frequently by social Darwinists, who claimed that inferior races displayed atavistic traits, and represented more primitive traits than their own race. Both the notion of atavism, and Haeckel's recapitulation theory, are saturated with notions of evolution as progress, as a march towards greater complexity and 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, 'throwback' traits that determined 'primitive' criminal behavior. His statistical evidence and the closely related idea of eugenics have long since been discredited, but the concept that physical traits may affect the likelihood of criminal or unethical behavior in the individual strangely still has some scientific support.^[10]

The notion that somehow, atavisms could be made to accumulate by selective breeding, or breeding back, led to breeds such as the Heck cattle. This had been bred from ancient landraces with selected primitive traits, in an attempt of "reviving" the extinct aurochs.

Cultural atavism

The term atavism is sometimes also applied in the discussion of culture.^[11] Some social scientists^[who?] describe the return of older, "more primitive" tendencies (e.g. warlike attitudes, "clan identity", anything suggesting the social and political atmosphere of thousands of years ago) as "atavistic". "Resurgent atavism" is a common name for the belief that people in the modern era are beginning to revert to ways of thinking and acting that are throwbacks to a former time. This is especially used by sociologists in reference to violence.^{[citation needed]}

The neo-pagan subculture also uses this same terminology ("atavism" or "resurgent atavism") to describe how modern, Western countries are experiencing both the decline of Christianity and the rise of religious movements inspired by the pagan religions of centuries past. Some cite the rise of environmentalism, scientific inquiry, and liberalization of society as contributing to an increasingly secular society, one in which religious sentiments are more frequently tied with an appreciation of the physical world rather than set against it.^{[citation needed]} Occasionally, the use of these terms in reference to "alternative" spirituality or in an occult context implies the use of violence to assert these changing religious views–for example, in the book Lords of Chaos a rash of church burnings across Scandinavia has been described as a part of this trend because many of the perpetrators were self-described "pagans" seeking to overthrow what they deemed to be centuries of religious oppression by Christianity.

Atavism is a key term in Joseph Schumpeter's explanation of World War I in 20th century liberal Europe. He defends a liberal view of international relations that an international society built on commerce will avoid war because of war's destructiveness and comparative cost. His reason for WWI is termed "atavism", in which he claims the vestigial governments in Europe (the German Empire, Russian Empire, Ottoman Empire, and Austro-Hungarian Empire) pulled the liberal Europe into war, and that the liberal structure of the continent 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 in nations who are built on commercial ties.

Hunter S. Thompson used the phrase "atavistic endeavor" in many of the pieces he wrote and the phrase is still strongly associated with him.

See also

• Atavistic regression
• Exaptation
• Spandrel (biology)
• Vestigiality

References

External links

Look up atavism in Wiktionary, the free dictionary.

• Photograph, X-ray and description of three cases of human tail
• Photograph of an additional (third) hoof of cows