Savanna anthropogenesis in the Mariana Islands, Micronesia: re-interpreting the palaeoenvironmental data (original) (raw)

2009, Archaeology and Physical Anthropology in Oceania

This paper argues that human actions had nothing to do with creating tropical Pacific island savannas, which likely arose during the Pleistocene, and that geographic factors such as soils, climate, and fire are responsible for their distribution and persistence in the Holocene. Palaeontological observations from the southern Mariana Islands, including charcoal particles, pollen, and spores in palaeosediments from Guam and Saipan, cited by archaeologists as evidence for human-caused savannas, are re-interpreted as a natural outcome of geo-climatic conditions. Archaeological and ethnographic findings, past climate proxies, and field studies in soil science are also brought to bear on the issue. The data and arguments presented in favor of natural causation of the Marianas savannas motivate a re-examination of proposals that purport to explain the presence of savannas elsewhere in the tropical Pacific. Implications for future research are drawn. '… to kill an error is as good a service as, and sometimes even better than, the establishing of a new truth or fact.' Charles Darwin (1809-1882) Given the continuing debate over whether the Pacific Islands grasslands, or savannas, are anthropogenic, this paper provides reasons for archaeologists to abandon the notion that prehistoric human actions were responsible for the development of grasslands, or savannas, in the Mariana Islands of Micronesia (Fig. 1), and it calls into question the appropriateness of anthropogenic savannas elsewhere in Oceania. It considers palaeoenvironmental data (fossil pollen, spores, and charcoal particles in wetland sediments) that have been cited as evidence for this view and argues that in order to include such palaeoenvironmental observations in models of the human past, extra care is needed to warrant their use as human behavioral proxies. The paper shows that such care is lacking in the proposal by Athens and colleagues that deliberate firing of 'pristine forests', presumed to have covered the southern Mariana Islands upon human entry, resulted in the rise and spread of savannas beginning by c. 4300calBP or even earlier (Athens and Ward 2004a, 2004b; Athens et al. 2004). A geoclimatic alternative to the Athens model of Marianas savanna anthropogenesis is offered below, supported by palaeosediment data generated during fieldwork by Athens and colleagues, as well as by observations from archaeology, ethnography, geography, and soil science with which the Athens model does not conform. The paper is organized as follows. First, current explanations for savanna formation, derived from mid-20th century theories of Pacific botanists F.R. Fosberg and J. Barrau and applied to the Pacific Islands, are presented and their problems indicated. Next, a recent proposal by archaeologist J.S. Athens and colleagues that also invokes prehistoric human actions to account for the savannas of the southern Marianas is reviewed and critiqued. A geoclimatic alternative then is outlined, with attention to its ability to account for observations that have been problematic for human-impact theories. The paper ends with suggestions for future research.