The great majority of humans today live in complex societies, which can exist only due to extensive cooperation among large numbers of individuals. Ultrasociality, the ability of humans to cooperate in large groups of genetically unrelated individuals, presents a puzzle to both evolutionary and social theory. Its emergence likely involved the evolution of cooperation in small groups – during which humans became much more egalitarian than their closest relatives, the great apes – followed by a reversal of this trend starting around 5–10 kya, with the rise of the first civilizations. Evolutionary biologists, political scientists, anthropologists, and others have proposed a multitude of theories explaining how complex societies evolved. However, these theories have largely relied on verbal reasoning. Until recently, formal models have focused on the evolution of cooperation in small groups, while the transition from small- to large-scale societies has been mostly neglected. The aim of this workshop is to bring together a diverse group of modelers and social scientists to (i) synthesize the state of knowledge in formal models of the evolution of social complexity, (ii) identify unresolved issues, and (iii) set an agenda for future collaborative work. The workshop will be organized around the following general themes: What data are available? What modeling techniques are available? What are the empirical patterns that cannot be explained by existing theories/data? How can we adapt existing models to fully use available data? What kind of data are needed to better inform the models? What new modeling techniques and methods need to be developed?
The great majority of humans today live in large-scale, complex (i.e. hierarchically organized) societies, which can exist only on a basis of extensive cooperation among large numbers of individuals. Ultrasociality , the ability of humans to cooperate in large groups of genetically unrelated individuals (Campbell 1983) presents a puzzle to both evolutionary and social theory (Richerson and Boyd 1998; see discussion in Turchin 2006: Chapter 5). The appearance of ultrasociality in human social evolution is analogous to major evolutionary transitions in biological evolution (Maynard Smith and Szathmáry 1995), such as the origin of chromosomes, multicellularity, and eusocial insects.
Multilevel selection theory provides a powerful conceptual framework for understanding major transitions in evolution (Sober and Wilson 1991, Okasha 2007, Wilson and Wilson 2007). Within this framework, the evolution of human ultrasociality can be viewed as occurring in two stages. The first stage likely involved the evolution of cooperation in small-scale groups (hundreds or, at most, a few thousand of people). Theories of how small-scale sociality evolved in humans are rapidly maturing. Potential mechanisms include (a) warfare, which intensified between-group selection; (b) inequity aversion and other leveling mechanisms (food sharing, monogamy, social control of “upstarts”), which reduced within-group variation in fitness and, thus, the strength of individual-level selection; (c) moralistic punishment, which suppressed free-riding, and (d) culture, which (via conformist transmission) reduced within-group variability and enhanced between-group variability. A number of models (mostly game theoretic) incorporating these mechanisms have been proposed and studied in detail (e.g. Sober and Wilson 1991, Wilson 2002, Boyd and Richerson 1985, Richerson and Boyd 1998, 2005, Bowles 2006, Choi and Bowles 2007, Turchin 2006, Lehmann and Feldman 2008).
The second stage, the evolution of true ultrasociality, was likely enabled by several additional key adaptations, including, for example, the capacity to demarcate group membership with symbolic markers (Shaw and Wong 1989, Masters 1998, Richerson and Boyd 1998) such as language and dialect, religion, clothing, and ornamentation, or the hierarchical organization of societies, which allowed unlimited growth in the scale of cooperating groups, simply by adding extra organizational levels (Turchin and Gavrilets 2009). Other key innovations include literacy and record keeping, formal legal systems, bureaucracies, organized religion, urbanization, and states. The primary mode of evolution was clearly cultural (Smith 2011), possibly with feedback loops between cultural and genetic evolution (Richerson and Boyd 2005, Hawks et al. 2007). Although ultimate evolutionary causes of the rise of social complexity are probably the same as in the first stage (and as in other major evolutionary transitions), the proximate mechanisms appear to be very different. Currently, there are only a handful of modelling studies focusing on the transition from small- to large-scale societies (e.g. Dacey 1969, 1974; Bremer and Mihalka 1977; Cusack and Stoll 1990; Cederman 1997, Spencer 1998; Turchin 2006; Cioffi-Revilla 2005; Cederman and Girardin 2010; Gavrilets et al. 2010 ); these studies primarily use simple models borrowed from mathematical ecology or agent-based simulations.
Our overall goal is to stimulate the development of a testable quantitative theory of the evolutionary transition to ultrasociality . Questions to be discussed at the workshop will include:
We aim at a true dialogue between modelers and empiricists. Fortunately, comparative data are already available in the anthropological literature to inform the model-building process and for empirical testing of model predictions, and other empirical initiatives are underway (e.g., Social Evolution Database). For example, Murdock and White's (1969) Standard Cross-Cultural Sample comprises coded data for approximately 2000 variables for 186 societies (White et al. n.d.) , including data on a society's scale and population density, subsistence strategies, kinship and marriage systems, division of labour, and degree of political integration. In modelling the transition from small- to large-scale societies, and the concomitant development of hierarchical social organisation, these data can be used to extract clusters of factors that co-vary with degree of political integration, and which may therefore have driven this transition. The processes inferred from the synchronic data in cross-cultural samples can then be tested against the diachronic data in archaeological databases. For example, Peregrine's (2003) Atlas of Cultural Evolution provides a score of “cultural complexity” for 289 archaeological traditions sampled through time, based on features such as degree of urbanisation, social stratification, political integration, and technological specialisation. Additionally, complete sequences of archaeological data for selected world regions can be used to investigate the extent to which the patterns and processes inferred from these world-wide samples generalise through time and space. Six such sequences are available through the eHRAF Archaeology database, namely the Highland Andean sequence, the Highland Mesoamerican sequence, the Mayan sequence, the Egyptian sequence, and the Mississippian sequence. Indeed, the future development of this field need not be limited to existing databases: one of the conference goals is to motivate archaeologists and anthropologists to develop other regional sequences in addition to the ones mentioned above. The dialogue between modelers and empiricists that we aim to foster through the proposed workshop will make any such efforts theoretically justified and empirically useful.