Dr. Chris O’Brien uses the
Archaeometric Lab’s microscopic
digital imaging system to analyze
a thin section.
The thin section is from a Dall
ram. The ram was 8.5 years
old when it was taken by a
hunter in Northwest
In this and four subsequent issues of Inside Chico State, I'll describe ongoing archaeological research activities developed and organized through five distinct facilities incorporated under the Anthropology Department umbrella: the Archaeometric Lab, the Zooarchaeology Lab, the Archaeological Research Program, the Northeast Information Center, and the Archaeology Laboratory. The Archaeology Lab is a central hub, supplying material needs, student work stations, processing and analysis facilities, and maintaining both the academic integration and public outreach dimensions of the entire program.
Chris O'Brien, Ph.D., University of Wisconsin 1994, joined the CSU Chico Anthropology Department as an adjunct professor in 1995, a neat trick because he also holds down a full-time job as assistant forest archaeologist with the Lassen National Forest. He has a broad archaeological background and training, and during the summer he can be found conducting archaeological surveys and excavations in Lassen and other forests nearby. But his special skills bring an important and fascinating dimension to the CSU, Chico archaeological studies program. O'Brien is one of a very few archaeologists specializing in dental increment analysis, a technique based on the study of tree-ring-like growth rings found in the teeth of large-bodied animals. While introduced and used most heavily by wildlife biologists, archaeologists have begun to employ dental increment studies to determine the age and season of death of animals found in archaeological sites. This kind of information can be used to reconstruct the season of use of sites, to characterize the properties of game herds exploited by prehistoric hunters, and even evaluate predator-prey dynamics expressed in the relationship between ancient human hunters and the game that they hunted. Once per week, Chris can be found in the Archaeo-metric Lab in Langdon Hall, often working with Anastasia Leigh, an Anthropology Department graduate student who is training with O'Brien while she completes her master's thesis on dental increment analysis.
Dental increment analysis requires a well-preserved tooth. Archaeological specimens are best retrieved from deeply buried deposits, rockshelters, or caves, all contexts which tend to provide the best conditions for preservation of organic remains. To conduct the analysis, the tooth is first identified as to species. The whole tooth is then mounted in an epoxy block which, when set, is cut to make a thin slice.
Additional grinding produces a readable thin section. A high-powered microscope and digital imaging system available in the Archaeometric Lab is used to isolate and define growth ring phenomena. O'Brien's active projects reveal the range of really interesting archaeological/ecological implications of dental increment findings. O'Brien is still pursuing and expanding his dissertation research, which spanned several field seasons in Kenya, East-Central Africa. His field work involved two components: 1) visits to a major game ranch to collect specimens representing documented kills from thoroughly managed herds, and 2) travel over the open countryside with a nomadic hunting band known as the Hadza in order to collect specimens from kills made by hunters seeking food for the band. In both contexts, O'Brien collected the teeth from big game kills, eventually collecting and analyzing over 1500 teeth representing seven game species (primarily zebra, wildebeest, hartebeest, and impala). The game ranch specimens provided a control group, taking advantage of tags and records to determine independently the precise season of death, and thus enabling him to calibrate the method. Currently, he is reexamining his field records to reveal and compare the dynamics of human-game interaction at both the game ranch and among the Hadza. He is convinced his data reveal that -- as a result of seasonal changes in game herds associated with calving and the predominance of certain age-sex herd groups, and seasonal changes in human take and technology associated with aggregation and dispersal patterns -- hunter-gatherers could generate a significant impact on the density and distribution of large game species.
O'Brien is offering additional training opportunities to Anthropology Department graduate students in connection with several ongoing projects:
An analysis of black-tailed deer teeth from archaeological sites located in the Ishi Wilderness.
An analysis of bison teeth from a late prehistoric "buffalo jump" site in Wyoming.
An analysis of bighorn sheep teeth for the California Department of Fish and Game.
An analysis of pronghorn teeth from an accidental kill location in Montana.
O'Brien and his wife were both raised in Paradise, and now live with their two children in Susanville. One of his main goals is to expand his activities at CSU, Chico, especially in the development of a dental increment contracting program that will provide service to off-campus parties such as wildlife managers and other archaeologists.
O'Brien hopes to increase CSU, Chico faculty, staff, and student research opportunities via the dental increment lab, as well as enhance the forest's image with the public by taking a more active role in the scientific understanding of forest resources.
For information about Archaeology Laboratory tours, please call Greg Whiteat 898-4360. Elementary and high school groups are welcome!
Greg White, Archeological Research Program and Anthropology