Population Growth and Human Behavioral Change

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Robert Kelly and his research team will investigate the relationships between environmental change and human population growth and decline on human behavior over a 12,000-year period in northwest Wyoming. With its ability to study long spans of time, archaeology is uniquely positioned to study, as in a laboratory, the impact of these two crucial variables on human societies. In doing so, this research helps determine if environmental change, including both long-term trends and short-term fluctuations, or human population density individually are sufficient to produce change in human behavior, or if the greatest change is produced by their combined effect. Given that world population will reach 11 billion by AD 2100, and on-going environmental changes, planning for the future should make use of the best laboratory available, deep human and environmental history. Three graduate students will assist in this analysis and use the site’s data for their dissertations. Continuing a long tradition, Kelly will use the site’s analysis in public lectures to discuss the impact of environment and population on human behavior.The project employs existing data, e.g., pollen cores from nearby lakes and a regional database of radiocarbon dates, to reconstruct environment and regional human population. The project’s main contribution is analysis of evidence of human behavioral change based on data recovered from an archaeological site, Alm Shelter, recently excavated by Kelly and his team in Wyoming’s Bighorn Mountains. Alm Shelter provides a 12,000-year record of human use, and, lying beneath an overhanging cliff, is dry and thus provides excellent preservation of organic materials. Often, the layers of earth that comprise a site have been disturbed, with artifacts moved about by burrowing animals or human activities such as digging pits. Thinking of an archaeological site as a book that one reads from the bottom up, such disturbances move paragraphs – artifacts and bones – from one chapter to another, making the book difficult to read. But that is not the case at Alm Shelter; this site’s layers are intact and accumulated at a slow rate that remained constant over time. This permits a unique analysis. Archaeologists use a statistical method known as an “age-depth model” to assign an age-range to artifacts based on their depth. Given this site’s careful excavation, a tight age-range can be assigned to literally every single artifact, bone, and other item recovered from the site. This allows a new analytical approach, one where the changing abundances of artifacts and other remains can be examined as distributions of age-ranges. These distributions can then be statistically analyzed to determine when different kinds of artifacts, such as projectile points, or different kinds of animal remains are changing in sync and how those changes relate to the known environmental and human population changes of the region’s past. Using artifacts, and discarded plant and animal remains as evidence of past human behavior, this analysis provides a way to examine how behavior changed in relation to environmental changes and human population density.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.