Original ArticleThe sequential evolution of land tenure norms
Introduction
Land tenure norms have long fascinated scholars of human society (de Laveleye, 1874, Engels, 1884, Maine, 1876, Morgan, 1877), as they define the relationship between people and the land, and the rules that regulate how the land can be used, possessed, and redistributed. Centuries of scholarship have painted a relatively clear picture of the diversity of land tenure norms, but a focused account of their evolution has yet to emerge. At the root of the problem is a lack of reliable historical accounts of land tenure transformations. Archaeological data may provide more depth, but it is often difficult to make direct inferences about land tenure norms (Earle, 2000). For these reasons, an alternative approach is necessary.
The bedrock upon which our understanding of the evolution of human cooperation and the transformation to large-scale societies must be grounded, land tenure norms provide a key to understanding other important aspects of human social evolution (Jordan et al., 2013). Land tenure norms are a prime example of niche construction (O'Brien and Laland, 2012, Shennan, 2011) as their evolution has shaped the nature of inequality and intergenerational transfers, restructuring the selective pressures facing early cultivators (Gibson and Gurmu, 2011, Kushnick, 2010, Voland and Dunbar, 1995). Further, the emergence of immovable property may have changed prevailing patterns of postmarital residence and an understanding of land tenure evolution is thus a crucial link in the chain of evidence needed to explain genetic diversity (Jordan et al., 2009, Oota et al., 2001, Wilkins and Marlowe, 2006).
Here we adopt a rigorous phylogenetic approach to modelling the evolutionary trajectories of land tenure norms in Austronesian societies (Gray et al., 2007, Mace and Pagel, 1994, Nunn, 2011). Our approach is multifaceted, and includes: (a) testing for phylogenetic and geographic signal in land tenure norms, (b) testing for relative support amongst competing linear and non-progressive models of evolution, and (c) reconstructing ancestral states. Developed in evolutionary biology, phylogenetic approaches have sometimes met skepticism when applied to understanding cultural evolution. Not least amongst these criticisms is that the approach assumes that norms are transmitted vertically, downplaying the possibility of independent invention (i.e., convergent evolution) and diffusion (i.e., horizontal transmission). Despite early detractors (e.g., Borgerhoff Mulder et al., 2006, Boyd et al., 1997), phylogenetic approaches have a growing body of empirical studies that attest to their utility (e.g., Currie, 2013, Gray et al., 2007, Mace and Jordan, 2011).
Austronesian-speaking communities are a particularly apt set of populations for addressing this issue. First, the Austronesian expansion saw groups spread through the Pacific in pulses and pauses (Gray, Drummond, & Greenhill, 2009), initially intermingling with pre-existing populations in Island Southeast Asia and New Guinea, and then to an array of virgin lands where the prevailing socioecological conditions might have selected for rapid cultural macroevolutionary diversification. Second, the predominantly island environments occupied by this group of societies can be seen as a “laboratory for the study of cultural adaptation” (Sahlins, 1958: x). Third, the group is largely composed of cultivators and, thus, land is central to their lifestyles; the common ancestral communities were likely to be societies of Neolithic farmers, and most of the descendant populations retain some sort of agrarian component (Diamond & Bellwood, 2003). Fourth and pragmatically, excellent language phylogenies are available, as are data on land tenure (Greenhill, Blust, & Gray, 2008).
Section snippets
Evolution of land tenure norms
Late 19th-Century explanations for diversity in land tenure systems were framed in terms of unilineal evolution (de Laveleye, 1874, Engels, 1884, Maine, 1876, Morgan, 1877). For instance, in de Laveleye (1874), societies progressed from a nomadic phase without land ownership, to agrarian pastoral phase within which land was held by groups with usufruct rights given to individuals. From there, they progressed into the agricultural phase within which land rights were held by patrilineal kin
Methods
We used computationally intensive phylogenetic methods (Gray et al., 2007, Mace and Pagel, 1994, Nunn, 2011) derived from evolutionary biology to reconstruct the evolution of land tenure norms among Austronesian societies. We adopted an approach to making inferences about ancestral states in changes in social organisation that Jordan et al. (2009) have dubbed “virtual archaeology”. In particular, we: (a) calculated phylogenetic signal for land tenure norms, and measured this against “geographic
Phylogenetic and geographic signal
Estimates of the D-statistic (Fritz & Purvis, 2010) over the posterior sample of 1000 lexical phylogenies for each land tenure norm are presented in Table 1. The values for group (G) were close to one (median = 0.87) and significantly different from zero, meaning that there is a lack of “clumping” of these norms on the tree i.e. they do not have strong phylogenetic signal. Values for I are also significantly different from zero and mostly greater than one (median = 1.19), indicating overdispersion,
Discussion
We used rigorous phylogenetic methods to model the evolution of land tenure norms in 97 Austronesian societies. By reconstructing the pattern of historical change in these societies, our analyses represent an important step toward understanding the bedrock of human society—one that transformed the selective landscape for Neolithic humans (Shennan, 2011) and paved the way for the evolution of cooperation, inequality, and large-scale society (Jordan et al., 2013). According to Sanderson (2007)
Supplementary Materials
The following is the Supplementary data to this article.
Acknowledgments
Thanks to Tim Earle, Mark McCoy, the attendees of the Biological Anthropology Seminar Series at the University of Washington, and two anonymous reviewers for useful feedback.
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