Geoarchaeology studies the connections between Earth and the human past. Geoscientists assist in the interpretation of the human past by helping to predict the location of archaeological sites, placing artifacts and archaeological features in the context of space and time, and investigating the connections between prehistoric humans and changes in physical environments and biotic communities. Recent studies illustrate the diversity of earth science approaches that researchers apply to the study of the human past, covering a wide variety of archaeological time periods and geo-environmental contexts.
Discovering the human past
Geoarchaeologists have developed tools to predict the location of contexts that may contain archaeological sites, including those home to Ice Age hunter-gathers or ancient cities. Rolfe Mandel of the University of Kansas has built a chronological framework for predicting the potential location of Paleoindian sites in the Central Great Plains. C. Russell Stafford of Indiana State University has used soil-geomorphic studies to predict the age and distribution of archaeological remains in the lower Ohio Valley. And Zhichum Jing of the University of British Columbia and Rip Rapp at the University of Minnesota-Duluth have applied studies of the alluvial deposits on the floodplains of the Yellow and Huan rivers in China to locate "lost" cities in China. Using core drilling they have now found palatial foundations at what was probably the Shang Dynasty capital city, Huanbei Shang City.
Time, space, and archaeology
Understanding the dynamics of archaeological change requires building temporal and spatial frameworks. Geoarchaeological studies have played a critical role in the study of the Big Eddy site in western Missouri that contains stratified Paleoindian and pre-Clovis-age sedimentary deposits. Ed Hajic at the Illinois State Museum, Rolf Mandel of the University of Kansas, and Art Bettis of the University of Iowa presented papers at the 2002 Society of American Archaeology (SAA) meeting on the stratigraphic, geomorphic and radiocarbon chronology of this important site. Similarly, a multidisciplinary approach has helped to develop an understanding of human adaptation and changing environments in the Great Basin during the last glacial-interglacial transition (G. Huckleberry, Quaternary Research, v. 55).
University of North Texas geoarchaeologist C. Reid Ferring and David Loedkipanidze of the Georgian State Museum have been studying a site in the Republic of Georgia containing Oldowan artifacts and fossils of Homo ergaster. Dated to about 1.7 million years ago, these fossils document one of the oldest, firmly dated occurrences of humans in Eurasia. Oldowan artifacts in Israel have also recently been dated to around 1.7 million years (H. Ron and S. Levi, Geology, v. 29). Stratigraphic and chronological studies also indicate that hominids were present in Southeast Asia by 840,000 years ago (P. O'Sullivan, Geology, v. 29).
Jim Feathers at the University of Washington has applied luminescence dating to study the southern end of the "ice free corridor" along the eastern front of the Northern Rocky Mountains. Proglacial (formed just in front of or behind a glacier) lake deposits connected with this potential migration route for late Pleistocene human groups have preliminary ages younger than the Last Glacial Maximum.
Julie Stein and William Farrand have recently edited a series of papers that summarizes the critical connections between depositional contexts and the archaeological record (Sediments in Archaeological Context, The University of Utah Press, 2001). A special issue of Geoarchaeology also addressed the site formation processes and archaeological record (v.17., 2002). In some situations, geoscientists have quantified relationships between proxy indicators of paleoecological landscapes and Pleistocene hominid behavior. Such is the case of 1.75 million-year-old wetland contexts associated with Early Stone Age artifacts at Olduvai Gorge, Tanzania (D. Decampo and others, Quaternary Research, v. 57, 2002).
Humans, climate, and extinctions
Intriguing studies have connected the record of the human past with dramatic changes in climates and landscapes, and have revealed links between humans and changes in biotic communities. One example is the possible relationship between prehistoric humans and Pleistocene mammal extinctions. A numerical simulation model appears to support the proposition that the end-Pleistocene megafaunal extinctions were a result of human hunting (J. Alroy, Science, v. 293). At the SAA meeting, Russell Graham of the Denver Museum of Natural History and collaborators presented evidence for a two-pulse extinction. They concluded that although the extinctions of mammoth and mastodon occurred at the same time that humans were hunting them, the extinctions were probably not directly related to human hunting. Dale Guthrie of the University of Alaska presented data supporting a model where changes in vegetation patterns from decreasing aridity led to extinctions. Similarly, the timing of human-mammoth interaction in Siberia indicates that human hunting probably had a limited influence on mammoth populations (V.N. Zenin and others, Nuclear Instruments and Methods in Physics Research B, v. 172, 2000).
The links between human populations, Holocene climate, and changes in landscapes have been the focus of geoarchaeological studies. Stalagmites in caves have provided a record of climate change in the southwestern United States that may help explain human adaptations over the last 4,000 years (V. Polyak and Y Asmeron, Science, v. 294; Geotimes, December 2001). Climate and human-induced disturbance, such as forest clearance resulting in soil erosion), has been linked to the archaeological record of the Maya in Guatemala (M. Rosenmeier and others, (Quaternary Research, v. 57, 2002). There has also been documentation of the influence of El Niño on Holocene environmental change and human activity in Peru (D. Sandweiss and others; F. Magilligan and P. Goldstein, Geology, v. 29, 2001).
These recent highlights show geoarchaeology can focus on studying the direct relationships between the record of past human behavior and Quaternary stratigraphy and geomorphology. More broadly, however, the discipline of geoarchaeology seeks to understand human-Earth connections.
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