Dual-tier approach to societal evolution and types Jill E. Neitzel a,⇑ , Timothy Earle b a Department of Anthropology, University of Delaware, Newark, DE 19176, USA b Department of Anthropology, Northwestern University, Evanston, IL 60208, USA article info Article history: Received 21 February 2014 Revision received 6 September 2014 Keywords: Societal evolution Societal types Political economy Chiefdoms Dual-tier approach Cross-cultural comparisons Polynesia North American Southeast North American Southwest Goldilocks moments abstract The dual-tier approach to studying societal evolution aims to identify both specific and general processes of prehistoric change that produced greater organizational complexity. The approach involves diachronic comparisons of archaeological sequences that represent typologically similar cases. Initial comparisons are done of historically related societies within world regions so as to define each region’s organizational variability for the type and time period being considered. This variability provides important contextual information for identifying exceptionally complex cases and understanding the reasons why they devel- oped. Next, comparisons are done of different regions’ singularly complex cases to identify similar, but historically independent, processes of societal evolution. Societal types guide the selection of appropriate world regions and exceptionally complex societies to compare. Focusing on chiefdoms, a classic evolu- tionary type that we define by polity population size, we illustrate the dual-tier approach with late pre- historic sequences from Polynesia and the North American Southeast and Southwest. We show that the different regions’ exceptionally complex cases were located in optimal environments where they experi- enced population growth, intensified resource procurement, expanded political economy, and formalized religious ideology. However, the relative importance and details of these trends varied considerably. Doc- umenting the ‘‘Goldilocks moments’’ that made organizational transformation possible offers a produc- tive means for future evolutionary studies. Ó 2014 Published by Elsevier Inc. 1. Introduction Evolutionary thinking in archaeology is now characterized by a dizzying array of approaches and perspectives that lack a common core of understanding. Healthy critiques and reformulations over the years have caused this fragmentation, but one constant and incendiary ingredient has been the use of societal types. We seek to move forward by looking operationally at how societal types remain necessary but must have a different role in evolutionary studies. Types originally served to classify contemporary societies with pseudo-histories of development, for which actual sequential data were lacking. The current growing body of archaeological data, however, makes diachronic comparisons both within and between areal sequences possible, and types have a role in comparisons that expose (rather than conceal) variability and transformational change. The premise of social evolutionism is that general processes shape societal change. For those that accept this premise, the task of identifying these general processes requires comparisons. Here we propose a dual-tier approach that provides a framework for studying evolutionary sequences. Its initial comparisons are done of historically related societies within world regions so as to define each region’s range of organizational variability, its typical or nor- mal pattern (what we call normalcy), and its exceptionally com- plex cases (what we call singularities). A region’s variability provides important contextual information for identifying its sin- gularities and understanding the reasons why they developed. Next, comparisons are done of different regions’ ranges of organi- zational variability, conditions of normalcy, and most complex cases. Similarities shared by more singularities in historically unre- lated regions can reveal more general evolutionary processes. To show how current archaeological approaches to social evolu- tionism became so fragmented and the value of the comprehensive framework provided by the dual-tier approach, we begin with a historical review of evolutionary thinking and societal types. We then illustrate the dual-tier approach for chiefdoms in three world areas. Given the typological confusion concerning chiefdoms, we define them and their variability using a single criterion—polity population size, which has the advantages of being quantifiable (and thus easily comparable) and of being linked to increased insti- tutional complexity needed to organize expanding scales. http://dx.doi.org/10.1016/j.jaa.2014.09.012 0278-4165/Ó 2014 Published by Elsevier Inc. ⇑ Corresponding author at: Department of Anthropology, University of Delaware, Newark, DE 19716, USA. E-mail addresses: neitzel@udel.edu (J.E. Neitzel), tke299@northwestern.edu (T. Earle). Journal of Anthropological Archaeology 36 (2014) 181–195 Contents lists available at ScienceDirect Journal of Anthropological Archaeology journal homepage: www.elsevier.com/locate/jaa