AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 68:555 (1985) Film Review Archaeological Dating: Retracing Time JEANNE E. ARNOLD Department ofSociology and Anthropology, University of Northern Iowa, Cedar Falls, Iowa 50614 Encyclopedia Britannica Educational Corporation, 425 Michigan Ave., Chicago, Illinois 60611, 1976. 16 mm color sound film, $315; video cassette, $250; rental, $13.90. 18 minutes. A variety of archaeological dating techniques commonly applied in North America and particularly in the American southwest are introduced in this film, beginning with the examination of different classes of materials that may lend themselves to relative chronological dating (ceramics and stone tools) and progressing to absolute dating techniques such as dendrochronology, archaeomagnetism, obsidian hydration, and radiocarbon dating. The principles of relative dating and stratigraphic analysis are introduced by Cynthia Irwin-Williams as she excavates at the prehistoric Salmon Ruin in New Mexico. IrwinWilliams identifies various materials recovered from a kiva within the ruin and shows how it and other structures may be relatively dated using such materials. In one instance, firm contemporaneity between a living floor within the ruin and part of the prehistoric sequence representing the Anasazi at Mesa Verde, Colorado, is established through pottery analysis. Next, the high-precision dendrochronological dating technique is explained. Dendrochronology has made possible the dating of many prehistoric structures in the southwest t o the exact year of construction. A dendrochronological sequence has been compiled using successively older wooden beams t o create a master tree-ring chart which is accurate to the year, extending back to 59 BC. This important dating method is clearly illustrated and several of its various applications are introduced. Archaeomagnetic dating of baked clay hearths is also illustrated briefly, as is the technique of obsidian hydration dating. The limitations of these two techniques are not discussed, perhaps to maximize the clarity of the presentation by reducing some of the real-world complexities, 0 1985 ALAN R. LISS. INC but it seems prudent nevertheless to alert viewers to certain difficulties in interpretation and potential margins of error in such approaches. To some degree this issue resurfaces in the film’s discussion of the most widely applied of all absolute dating techniques, radiocarbon dating. This method is described in a manner that emphasizes the laboratory processing of the organic sample and the apparatus used in measuring Carbon-14. More could be said about the fundamental reasons the radiocarbon technique works and, again, some of the problems we have with dates obtained by this method. In spite of this minor philosophical difference about what ought and ought not be mentioned in the educational presentation of dating methods, 1 recommend this film very highly. It is clear, superbly photographed and edited, and the package presented to the viewer is a satisfying one. The various materials from the Salmon Ruin provide an AD 1061 tree-ring date, an AD 1095 archaeomagnetic date, an AD 1095 obsidian hydration date, and an AD 1100 (+70) radiocarbon date. The high quality of the archaeological fieldwork conducted by Irwin-Williams is evident and her dedication and that of her crew to careful analysis of materials from this site provide an excellent model for beginning students. In particular, high school students and university students in introductory physical anthropology and archaeology classes will find this film useful and interesting. In some cases, instructors might choose to supplement a showing of the film before or after with remarks on difficulties and limitations of dating techniques. Instructors of advanced students of archaeology may find the introductory nature of the film to be inappropriate for their classes.