Migrationism and diffusionism
In the history of archaeological theory the term migrationism was opposed to the term diffusionism (or "immobilism") as a means of distinguising two approaches to explaining the spread of prehistoric archaeological cultures and innovations in artefact. Migrationism explains cultural change in terms of human migration, while diffusionism relies on explanations based on trans-cultural diffusion of ideas rather than populations (pots, not people).
Western archaeology the first half of the 20th century relied on the assumption of migration and invasion as driving cultural change. This was criticized by the processualist in the 1960s and 1970s, leading to a new mainstream which rejected "migrationism" as outdated. Since the 1990s, there has been renewed interest in "migrationist" scenarios, as archaeologists attempted the archaeological reflexes of migrations known to have occurred historically. Since the 2000s, the developments in archaeogenetics have opened a new avenue for investigation, based on the analysis of ancient DNA.
In British archaeology, the debate between "migrationism" and "immobilism" has notably played out in reference to the example of the Anglo-Saxon settlement of Britain.
"Diffusionism" in its original use in the 19th and early 20th century did not preclude migration or invasion. It was rather the term for assumption of any spread of cultural innovation, including by migration or invasion, as opposed "evolutionism", assuming the independent appearance of cultural innovation in a process of parallel evolution, termed "cultural evolutionism".
Opposition to migrationism as argued in the 1970s had an ideological component of anti-nationalism derived from Marxist archaeology, going back to V. Gordon Childe. Childe in the interwar period combined "evolutionism" and "diffusionism" in arguing an intermediate position that each society developed in its own way, but strongly influenced by the spread of ideas from elsewhere. In contrast to Childe's moderate position, which did allow the diffusion of ideas and even moderate migration, Soviet archaeology adhered to a form of extreme evolutionism, which explained all cultural change due to the class tensions internal to prehistoric societies.
"Migrationism" fell from favour in mainstream western archeology in the 1970s. Adams (1978:483f.) described migrationism an "ad hoc explanation for cultural, linguistic, and racial change in such an extraordinary number of individual cases that to speak of a migrationist school of explanation seems wholly appropriate". Adams (p. 484) argued that the predominance of migrationism "down to the middle of the last [19th] century" could be explained because it "was and is the only explanation for culture change that can comfortably be reconciled with a literal interpretation of the Old Testament", and as such representing an outdated "creationist" view of prehistory, now to be challenged by "nonscriptural, anticreationist" views. Adams (p. 489) accepts only as "inescapable" migrationist scenarios that concern the first peopling of a region, such the first settlement of the Americas "by means of one or more migrations across the Bering land bridge" and "successive sweeps of Dorset and of Thule peoples across the Canadian Arctic".
While Adams criticized the migration of identifiable "peoples" or "tribes" was deconstructed as a "creationist" legacy based in biblical literalism, Smith (1966) had made a similar argument deconstructing the idea of "nations" or "tribes" as a "primordalistic" misconception based in modern nationalism. 
The support of "diffusionist", i.e. non-migrationist, views has thus been associated with anti-nationalism and progressivism since the 1970s. While mainstream western archaeology maintained moderate scenarios of migrationism in spite of such criticism, it did move away from "invasionism". The mainstream view came to depict prehistoric cultural change as the result of gradual, limited migration of a small population that would consequently become influential in spreading new ideas but would contribute little to the succeeding culture's biological ancestry. Thus, the mainstream position on the Neolithic Revolution in Europe as developed (notably by German archaeologist Jens Lüning) since the 1980s, posits that "a small group of immigrants inducted the established inhabitants of Central Europe into sowing and milking" in a process spreading "in swift pace, in a spirit of 'peaceful cooperation'" Migration was generally seen as being a slow process, involving family groups moving into new areas and settling amongst the native population, described as "demic diffusion" or "wave of advance", in which population would be essentially sedentary but expand by the colonisation of new territory by succeeding generations.
The question remained intractable until the arrival of archaeogenetics since the 1990s. The new field's rapid development since the 2000s has resulted in an increasing number of studies presenting quantitative estimates on the genetic impact of migrating populations. In several cases, this has led to a revival of the "invasionist" or "mass migration" scenario (in the case of the Neolithic Revolution in Europe), or at least suggested that the extent of prehistoric migration had been underestimated (e.g. in the context of Indo-European expansion, it was estimated that the people of the Yamnaya culture in Eastern Europe contributed to 73% of the ancestry of individuals pertaining to the Corded Ware culture in Germany, and to about 40–54% to the ancestry of modern Central & Northern Europeans.)
- Carol Kramer, "Pots and Peoples" in; Louis D. Levine and T. Culyer Young (eds.), Mountains and Lowlands: Essays in the Archaeology of Greater Mesopotamia; Malibu, Undena, 1977; cited in Serge Cleuziou, "Introduction", Objets et symboles: de la culture matérielle à l'espace culturel : actes de la 1re Journée doctorale d'archéologie, Paris, 20 mai 2006, ed. Laurent Dhennequin, Guillaume Gernez and Jessica Giraud, Paris: Sorbonne, 2009, ISBN 9782859446222, p. 18, n. 12.
- Processual archaeology was further deconstructed by "Post-processual archaeology" which denied the possibility of ever forming objective conclusions based on archaeological evidence and denounced "materialist interpretations of the past" as being ethically and politically irresponsible.
- "The Danish archaeologist Kristiansen (1989) has suggested that the reasons for the rising popularity of immobilism lie in post-war decolonialisation and in the development of the welfare state. In the public realm, this led to an emphasis on political evolution rather than military solutions; in archaeology, this was translated into a belief in autochthonous development rather than 'invasions'." Härke (1998), citing Hills, C., "The Anglo-Saxon settlement of England. The state of research in Britain in the late 1980s", in: Ausgewählte Probleme europäischer Landnahmen des Früh- und Hochmittelalters, ed. M. Müller, (1993), p. 310.
- "it was assumed that technologies develop because of internal contradictions within societies. This required that in any explanation of cultural change the principal emphasis had to be on the development of society. The standard series of technological ages was replaced by a unilinear sequence of social stages, each of which was characterised by distinctive productive forces, relations of production, and ideology. [...] Migration was ruled out as a mode of explaining changes in the archaeological record, and strong emphasis was placed on independent parallel development." Trigger, Bruce, Gordon Childe: Revolutions in Archaeology (1980), p 93
- Anthony D. Smith, The Ethnic Origins of Nations (Oxford, 1966) pp. 6ff, coined the term "primordalistic" to separate these thinkers from those who view ethnicity as a situational construct.
- Matthias Schulz, Neolithic Immigration: How Middle Eastern Milk Drinkers Conquered Europe, Spiegel Online (2010).
- Zimmer, Karl (June 10, 2015). "DNA Deciphers Roots of Modern Europeans". New York Times.
- "Nomadic herders left a strong genetic mark on Europeans and Asians", 10 June 2015, By Ann Gibbons, Science (AAAS)
- Adams, W Y; Gerven, D P V; Levy, R S (October 1978). "The Retreat from Migrationism". Annual Review of Anthropology 7: 483–532. doi:10.1146/annurev.an.07.100178.002411.
- John Chapman, Helena Hamerow, (eds.), Migrations and Invasions in Archaeological Explanation, Archaeopress, 1997, ISBN 9780860548577.
- Kleinschmidt, Harald. People on the Move: Attitudes toward and Perceptions of Migration in Medieval and Modern Europe. Westport, Conn.: Praeger, 2003. Print.
- Heinrich Härke, Archaeologists and Migrations, Current Anthropology Vol. 39, No. 1 (February 1998), pp. 19-46.
- Finneran, N (2003). "The persistence of memory: national identity and migrationism: a case study from African and Ethiopian archaeology". Studies in Ethnicity and Nationalism 3: 21–37. ISSN 1473-8481.
- "Research History Relating to the Adoption and Expansion of Agrarian Practices and Societies". Acta Archaeologica 85 (1): 11–29. 2014. Retrieved 1 March 2015.
- Stratum (linguistics)
- Pre-modern human migration
- List of invasions
- Invasions of the British Isles
- Indo-European expansion
- Kurgan hypothesis
- Doric invasion
- Nomadic empire
- Turkic expansion
- Mongol invasions