Synchronous environmental and cultural change in the prehistory of the northeastern United States

Abstract

Climatic changes during the late Quaternary have resulted in substantial, often abrupt, rearrangements of terrestrial ecosystems, but the relationship between these environmental changes and prehistoric human culture and population size remains unclear. Using a database of archaeological radiocarbon dates alongside a network of paleoecological records (sedimentary pollen and charcoal) and paleoclimatic reconstructions, we show that periods of cultural and demographic change in the northeastern United States occurred at the same times as the major environmental-climatic transitions of that region. At 11.6, 8.2, 5.4, and 3.0 kyr BP (10(3) calendar years before present), changes in forest composition altered the distribution, availability, and predictability of food resources which triggered technological adjustments manifested in the archaeological record. Human population level has varied in response to these external changes in ecosystems, but the adoption of maize agriculture during the late Holocene also resulted in a substantial population increase. This study demonstrates the long-term interconnectedness of prehistoric human cultures and the ecosystems they inhabited, and provides a consolidated environmental-cultural framework from which more interdisciplinary research and discussion can develop. Moreover, it emphasizes the complex nature of human responses to environmental change in a temperate region.

Fig. 1.

Location of study region in relation to modern Canada and the United States (inset). Left: Location of sedimentary pollen (circles) and charcoal (squares) records; see Tables S1 and S2 for description of records and citations. Right: Location of archaeological radiocarbon dates used in this study; one point may contain multiple dates.

Fig. 2.

Associations between archaeological, climate, and vegetation records for the study region from initial settlement (13,500 yr BP) to European contact (500 yr BP). A stacked temporal frequency distribution of archaeological radiocarbon dates (bottom) provides information on the timing of cultural transitions and human population fluctuations. Lake-level (24) and temperature (23) reconstructions for the region provide a record of late glacial and Holocene climate. The mean of between-sample SCD values from the highest quality pollen records in the study region provide a measure of vegetation change through time. The CD between adjacent bins of archaeological radiocarbon dates provides a measure of the timing and rate of cultural change. Climate phases and transitions derived from paleoenvironmental data are based on Shuman et al. (7). Gray vertical lines denote cultural transitions defined from the frequency of archaeological ¹⁴C dates.

Fig. 3.

Regional-scale pollen and charcoal records in relation to cultural periods and population size. The mean (line) and standard deviation (envelope) of pollen and charcoal records at 250-year intervals are shown. Charcoal records were rescaled between 0-1 to produce a CI. Solid gray vertical lines denote cultural transitions and dashed line indicates the approximate beginning of maize agriculture in the region (39). Changes in regional human population size, also rescaled from 0-1, were estimated from radiocarbon data (silhouette); this reconstruction was also corrected for taphonomic bias (line) using the empirical model developed by Surovell et al. (30).