Islands as Model Environments

INTRODUCTION

Islands have long been important locales for the study of ecology and evolution. This utility stems from several distinctive characteristics of islands, such as their inherent boundedness, relative isolation, and biogeographical variability. In addition, many of the world's island regions were colonized by populations from similar mainland areas who then diversified along several dimensions of biological and cultural variability. As such, the evolutionary histories of human populations on islands offer unique opportunities for exploring the causes and consequences of biocultural diversity and human interaction with natural environments (Kirch 1997). Early discussions of the importance of islands for archaeology focused on viewing them as “natural experiments” or “cultural laboratories” where we could study cultural change in supposedly controlled, isolated environments (e.g., Clark and Terrell 1978; Evans 1973, 1977; Goodenough 1957; Keegan and Diamond 1987; Kirch 1986; Mead 1957; Sahlins 1955; Vayda and Rappaport 1963). This view of islands as laboratories has, however, been contested (e.g., Boomert and Bright 2007; Fitzhugh and Hunt 1997; Rainbird 1999; Terrell et al. 1997), namely on the grounds that few islands were ever truly isolated (see Fitzpatrick and Anderson 2008). In recent years, island archaeologists have reformulated the approach as one that instead views island environments and the histories of their prehistoric populations as models of coupled human and natural systems, or human ecodynamics (Kirch 2007a, 2007b; Rick et al. 2013; Vitousek 2002). This special issue continues in this vein and includes several papers on the uses of islands as model environments with case studies in the Pacific, Mediterranean, and Caribbean.

ISLANDS AS MODELS

Scientific models serve as simplified representations of a pattern or process to aid in the explanation of the empirical world. Although islanders are no more simple or complex than their continental counterparts, there are several characteristics of islands that make the conception of them as model environments especially salient. First, the nature of islands as particularly discrete and circumscribed terrestrial landscapes render them as distinct and simplified forms of more general kinds of habitat patches (Terrell 1999). This combination of inherent boundedness and the tremendous biogeographical variability of island sizes, climates, geologies, and marine and terrestrial ecologies provides a plethora of arrangements of environmental parameters in spatially delineated units. Comparative documentation and explanation of the varied prehistoric outcomes in these different environmental configurations yields model case studies of human ecodynamics (Kirch 1997, 2007a). Second, the relative isolation of islands from the mainland causes there to be a clear “starting point” for their prehistories, providing a definite temporal unit to explore the settlement of and adaptation to new landscapes (although we note that, with regard to specifics, the issue of initial colonization as opposed to exploitation or seasonal occupation is, for many islands, still a matter of contention or sub judice [e.g., Dawson 2014 for the Mediterranean]). Third, relative isolation has often resulted in generally low-diversity, comparatively responsive, and thereby vulnerable native biota, providing unrivaled opportunities for studying impacts on variable ecosystems (Anderson 2002; Fitzpatrick and Keegan 2007; Kirch and Hunt 1997; Losos and Ricklefs 2010; MacArthur and Wilson 1967; Rick et al. 2013). In sum, the often clear spatial and temporal boundaries of island environments and their prehistories, coupled with the varied mixture of physical and ecological parameters, result in suitable (or even ideal) model environments for archaeological analyses.

CONTRIBUTIONS TO THE SPECIAL ISSUE

The articles presented in this special issue examine many of these uses of islands as model systems. The contribution by Anderson (2018) focuses on the very early human dispersal into the Western Pacific and offers a compelling argument that initial colonization can be most parsimoniously explained using a simple model of ecological contingency—this research clearly has broader implications for pre-Holocene maritime dispersal more widely (see Dennell et al. 2014; Runnels 2014). Cherry and Leppard (2018) synthesize current data on the initial pre-Neolithic settlement of the Mediterranean and explore the biogeographical patterns and strategies for Neolithic colonization of new environments. Their study, as well as the contributions by Ramis (2018), Pilaar Birch (2018), and Giovas (2018) provide examples of how the often low terrestrial biodiversity of islands can make them marginal for human subsistence, often necessitating the translocation of non-native plant and animal foods, or so-called “transported landscapes.” Ramis (2018) and Pilaar Birch (2018), working at opposite ends of the Mediterranean, nonetheless underscore in their contributions the relative elasticity of Old World agropastoralism (as contrasted with late hunter-gatherer lifeways), permitting flexible adaptations to some of the Mediterranean's most marginal islands, leading to the emergence of truly anthropogenic biophysical systems. Issues of human impacts are also taken up in the articles by Harris and Weisler (2018) and Giovas (2018). Harris and Weisler (2018) review both modern and archaeological studies on human impacts on marine mollusks and provide an important contribution to research on the effects of human predation on coastal ecosystems. Similarly, Giovas (2018) synthesizes recent research on the island of Carriacou in the Caribbean and documents a complex interplay of human impacts, sustainable resource use, and responses to climatic uncertainty. In addition to the contributions by Giovas (2018) and Harris and Weisler (2018), DiNapoli et al. (2018) also provide a comparative examination of human adaptations to small island ecosystems, in particular environmental influences on cooperation and competition over limited resources.

CONCLUSION

Although island archaeology has moved beyond the simplistic “islands as laboratories” view, islands continue to be used as models for coupled human and natural systems, or human ecodynamics. Island environments have the potential to serve as useful case studies for a range of important topics in world prehistory, especially when approached comparatively. The articles in this issue demonstrate the potential of islands as models for broader archaeological topics, such as historical ecology, population dispersals, interaction, subsistence change, conflict and territoriality, impacts on native biota, and sociocultural evolution. They also, we suggest, hint at how processes, which have been enacted in miniature on islands throughout the Holocene, may operate on a global scale. It is not inaccurate to suggest that the dynamics of the current planetary biodiversity crisis (Ceballos et al. 2015) parallel, albeit on scales separated by orders of magnitude, microcosmic invasion/extinction processes on islands during human colonization. At a time in which archaeology must loudly and explicitly re-state its relevance and its connections to research questions that cross academic boundaries, our ability to understand the social and cultural repercussions of ecodynamic processes (rather than artificially separating historical ecology from political ecology) in comparative terms will be vital. On that basis, we optimistically note that in a recent review of island archaeology, Fitzpatrick et al. (2015) note the use of the ‘model environments' framework as one of the main developments in the field over the last 10 years, and we hope this volume stimulates further development of this framework in the years to come.

ACKNOWLEDGEMENTS

We thank Scott M. Fitzpatrick and Todd Braje for inviting us to guest edit this special issue of JICA, and to all the participants of the 2016 Society for American Archaeology symposium in Orlando, FL, titled “Model Environments: Human Ecodynamics on Islands.”