- 1a : recurrence in an organism of a trait or character typical of an ancestral form and usually due to genetic recombination
- b : recurrence of or reversion to a past style, manner, outlook, approach, or activity <architectural atavism>
- 2: throwback
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. 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.
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.
Social scientists 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.
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. 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 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.