Assessing the Role of Ecological Change on Economic and Demographic Transformations Between the Late Neolithic and Early Bronze Age in the Sizandro River Valley, Portugal

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With National Science Foundation support, Dr. Katina Lillios (University of Iowa) will lead an interdisciplinary team of US, Portuguese, and German researchers in a three-year archaeological project to determine what caused the collapse of complex societies around 2200 BC in the Sizandro River valley, west-central Portugal. The Sizandro River Valley Project brings specialists from archaeology, biological anthropology, and geoarchaeology to study the economic and demographic changes experienced by the ancient communities of the Sizandro River valley. During the Late Neolithic, the Sizandro valley was home to a thriving population, who lived in large fortified settlements and buried their dead in collective tombs. Trade goods that originated in the Portuguese interior and as far away as North Africa have been found in Late Neolithic sites along the Sizandro. During the Early Bronze Age (2200-1500 BC), many settlements were abandoned, and long-distance trade declined. During this same time, the sheltered estuary at the mouth of the Sizandro shrank as sea level fell, accelerated by hillslope erosion attributed to intensive Late Neolithic agriculture. Loss of the estuary might have cut the valley off from maritime trade, and silting of the river might have impeded trade with the interior. Estuarine resources dwindled and disappeared, and riverine ecosystems were transformed. However, the causal relationship between these ecological changes and the abandonments and collapse has never been tested. The Sizandro River Valley Project will contribute to a better understanding of the history of complex societies, including their collapse, by providing a detailed case study of one such collapse. It will also broaden the range of social and ecological contexts within which collapse has been studied. Most studies of collapse have been focused on vulnerable environments, such as the Classic Maya collapse in AD 900 in the rainforests of Central America, and the AD 1300 collapse in the American Southwest. Without broader knowledge, scholarly and popular understandings of climate change and societal collapse will remain limited. In order to evaluate the relationship between ecological change and social collapse in the Sizandro Valley and, ultimately, understanding of the regional transformations that occurred in Portugal, Dr. Lillios and her team will study mobility, diet, and settlement patterns. Specialists will analyze human skeletal remains and their bone chemistry from sites dated to prior to and post collapse. The team will also conduct excavations at the Late Neolithic-Early Bronze Age burial of Bolores to collect additional skeletal material. To assess changes in settlement pattern and their economic significance, team members will carry out two seasons of survey. Sites will be mapped, tested, and dated to more precisely characterize the changes in settlement pattern between the Late Neolithic and Early Bronze Age. The Sizandro River Valley Project will provide valuable educational opportunities for students and will strengthen working partnerships between US, Portuguese, and German archaeologists. Results will be broadly disseminated in scholarly publications, conference presentations, digital databases, public lectures, and classes. Project members will also share their findings in Portugal with local citizens, tourists, and schoolchildren.