The discoveries made over the last thirty years have revealed that sites surrounded by ditches and palisades – the enclosures – were an integral part of the Neolithic in Western Europe. These features are, however, neither ubiquitous nor permanent but they develop with different types, at different periods and in different regions according to historical evolutions and complex spatial and temporal dynamics. Between about 4200 and 3600 cal BC, the enclosures assigned to the "Michelsberg" culture(Gleser 1998 ; Lichardus 1998 ; Lüning 1967 ; 1998 ; Grund 2008) are distributed between France, Belgium and Germany, from the center of the Paris Basin to the Saale river. They mirror one of these moments in recent European Prehistory during which social institutions seem to emerge, triggered by increasing integration and interaction of the human groups, by an enlarged territoriality and by the reinforcement of social boundaries (Lichardus 1998 ; Schier 1993 ; Zimmermann et al. 2005).
Through excavations and survey we currently know several dozens of these enclosures and "fortifications" amongst the hundreds probably widely distributed over this large geographic area at that period. In addition to a possible settlement role, most of these sites (Matuschik 1999 ; Seidel 2006) indicate the presence of non- domestic activities (Bertemes 1991). More particularly, the "monumental" enclosures reveal strong and complex relationship with burial or in a more general way with "ceremonial" activities (Andersen 1997 ; Meyer, Raetzel-Fabian 2006). The catchment areas of these particular places, as well as the involved economic and social aspects have, however, to be analyzed more in detail.
A specific cultural process rooted in mesolithic-based danubian neolithization can be recognized in the pottery and lithic productions and it connects the different regions under study (Paris Basin, Wallonia, Rhine Basin, Hesse and Lower Saxony, Thuringia). Nonetheless, large opening to the neighbouring cultural groups is thought to be linked to this process, characterizing its involvement in a wider dynamics on the pan-European scale, which is formalized under the label "chalcolithization".
The appearance and the subsequent disappearance of the Michelsberg enclosures within a few centuries thus constitutes one of the most striking historical evolutions accompanying the adaptation of the European agricultural communities to multiple and differentiated ecological, climatic and demographic constraints. The environmental impact and its variations on this process have yet to be evaluated accurately, and so has the one of climatic change. This latter, studied in detail in the perialpine regions, appears to be clearly crucial at distinct moments in the course of the 5th and 4th millennium and may have accompanied the breakdown of the Michelberg culture (Arbogast et al. 2006). Concerning the demographic burden, it appears that the initial neolithic demographic pressure was progressively substituted by demographic pressure on the (sub)regional scale requiring the establishment of social and political entities able to manage the ever more important economic and social mechanisms (Bocquet-Appel 2002, Petrasch 2005, Shennan 2008).
Apparently, the enclosures reflect a more complex social and political organization required by the development of farming and stockbreeding economy, institutionalized within the material culture and formalized in the landscape. Advancing the plausible hypothesis that the flow of social relationships, as well as internal and inter-communal conflicts have increased with the enlargement of the area of social integration, the enclosures – particularly the most invested in terms of time, material and energy – would mirror at the same time both faces of social interaction (Schier 1993): the peaceful one, related to cooperation between social groups and the violent one, related to competition between groups.
The question of political and logically also the one of social hierarchy arises almost automatically within this issue, notably with regard to the control of strategic resources (water, soil, forest, lithic raw materials, salt…).
Social and political hierarchy in complex chiefdom societies in North America (Early Historic), a possible model of organization advanced for the Michelsberg sites in the Rhine basin (D. Gronenborn).
Additional hierarchical model of the Michelsberg sites in the Aisne valley (J. Dubouloz).
The interpretation of the neolithic enclosures has evolved according to the theoretical and ideological movements that have marked the last forty years: to a « materialist » approach, focusing on economic roles like exchange and defense, was added a sociological interpretation based on the political and social implications of the labour invested in these constructions thus becoming a proxy variable of social complexity and political evolution (Renfrew 1974). A relativistic conception, mainly Anglo-Saxon, then emerged during the 1980s, focusing on the multiform ideological and symbolic role of such « monuments », notably with regard to the issue of identity and collective memory (Hodder 1990 ; Whittle 1996 ; Darvill, Thomas 2001). In the 1990s, anthropology of violence and warfare enters the debate (Keeley 1996 ; Chapman 1999 ; Mercer 1999), prior to the recently introduced argument of environmental and climatic impact on the first farming and stockbreeding societies (Magny 2004 ; Arbogast et al. 2006 ; Gronenborn 2007). Yet, all these aspects, obviously interlinked in the prehistoric reality, have to be interconnected.