Henri Claessen has devoted much of his scholarly career to the study of Early States. The concept of the early state introduced by Henri J. M. Claessen and Peter Skalník appears to have been the last among the great epoch-making political-anthropological theories of the 1960s and 1970s. Claessen's thesis, Of Princes and Peoples, a comparative study of the political organization of five Early States where the emphasis came to be the central political organisation, which has remained an important theme in much of Claessen's work, lay at the basis of The Early State which he edited with Peter Skalník. In 1981, again with Peter Skalník, he edited The Study of the State. In later years he edited with M. Estellie Smith and Pieter van de Velde Development and Decline . In this work the emphasis fell on evolutionary aspects of state formation. With Pieter van de Velde he edited in 1987 Early State Dynamics, and in 1991 Early State Economics. To connect matters of ideology and legitimacy, he edited with Jarich G. Oosten in 1996 Ideology and the Formation of Early States. In his Structural Change was given a survey of evolution and evolutionism in Cultural anthropology. With Renée Hagesteijn and Pieter van de Velde he edited a special issue of Social Evolution & History under the title Thirty Years of Early State Research. Apart from a number of publications in Dutch, he contributed articles in English on traditional Polynesia in Bijdragen tot de Taal-, Land- en Volkenkunde, and articles on evolutionism in Social Evolution & History where he is a member of the Editorial Council.
Claessen's school developed a "Complex Interaction Model" to explain the evolution of sociopolitical organization and early state formation. According to the model factors such as ideology, economy and societal format become aligned in ways which favour state organisation.
Not only the number of people was relevant, but also the number of people in relation to the means of production, and the spatial distribution of the population, which both played a role in the evolution of socio-political organization. We therefore coined the term societal format, which covers the number of people, possible population pressure, and spatial distribution)
Selected works
1978. The Early State: A Structural Approach. In Claessen, H. J. M., and Skalník, P., The Early State. The Hague: Mouton.
1981. Specific Features of the African Early State. In Claessen, H. J. M., and Skalník, P., The Study of the State. The Hague: Mouton.
1983. Evolutionary or not evolutionary; That's the question. Reviews in Anthropology 10: 21-24
1984. The Internal Dynamics of the Early State. Current Anthropology 25: 365–379
1985. From the Franks to France; The Evolution of a Political Organization. In Claessen, H. J. M., van de Velde, P., and Smith, M. E., Development and Decline. South Hadley, MA: Bergin & Garvey.
1989. Evolutionism in Development. Vienne Contributions to Ethnology and Anthropology 5: 231–247.
1991. Verdwenen koninkrijken en verloren beschavingen . Assen: Van Gorcum.
1996. Ideology and the formation of early states: Data from Polynesia. In. H. J.M. Claessen and J. G. Oosten, Ideology and the formation of early states. Leiden: Brill.
2000. Structural Change; Evolution and Evolutionism in Cultural Anthropology. Leiden: CNWS Press.
2002. Was the State Inevitable? Social Evolution & History 1 : 101–117 .
2005. Early State Intricacies. Social Evolution & History 4: 151–158 .
2006. with Martin A. van Bakel: Theme and variations. The development of differences in Polynesian socio-political organizations. In: Bijdragen tot de Taal-, Land- en Volkenkunde. 162:218-268.
2008. Before the Early State and After. Social Evolution & History 7: 4–18 .
2009. Learning and training. Education in eighteenth century traditional Polynesia. In: Bijdragen tot de Taal-, Land- en Volkeknkunde 165: 324-356.
2011 On Chiefs and Chiefdoms In: Social Evolution and History 10 .
2011 Reconsideration or a Reformulation. In: Social Evolution and History 11 .
Claessen, H. J. M. & P. Kloos. Evolutie en evolutionisme.
Claessen, H. J. M. & P. van de Velde. Een intercultureel model voor het feodalisme. In: Evomatica, ed. by Pieter van de Velde, pp. 203–215. Leiden: Institute of Cultural Anthropology Publication 42.
Claessen, H. J. M. & P. van de Velde. Complexe interactie. Een process-model ter verklaring van de evolutie van de sociaal-politieke organisatie''. Antropologische Verkenningen 3: 120-136.