Using Science to Revive Old Excavations

Guest Blog by Professor Bill Lipe Professor Emeritus, Washington State University; Member of the Board of Directors, The Archaeological Conservancy

The value (and excitement) of archaeological field work doesn’t end when the pits are backfilled, the artifacts are analyzed, and the reports written.  At least that’s true if the collections are safely curated in a well-run museum.  Specimens collected long ago can often be revisited with new research methods to reveal new information of scientific and educational value. This is why archaeologists save archaeological collections long after they were initially studied.  Here, I give two examples of recent scientific analyses of specimens from one of the first excavations I ever directed.

Benchmark Cave

In 1958, during my first season as a crew chief, I directed excavations at Benchmark Cave, a small natural shelter in the Glen Canyon of the Colorado River, in southeastern Utah (Lipe 1960). This was part of the Glen Canyon project, designed to gain information about the archaeological record of sites that would be destroyed as Lake Powell formed behind the Glen Canyon Dam.  What initially appeared to be a small site turned out to be larger and much deeper than anticipated, so there were additional excavations in subsequent years. Benchmark Cave (named after a nearby surveyor’s marker) appears to have served for several thousand years as an occasional camping spot (Geib 1996).  In 1958, my crew excavated (from relatively recent levels) the two informative artifacts discussed below. The artifacts are curated at the Museum of Natural History of Utah in Salt Lake City, along with other materials from the Glen Canyon Project.

The Salt Cache

Within the shelter, the upper part of the archaeological deposit had remained dry.  Not far below the surface, in a stratum that had Ancestral Pueblo potsherds of styles common in the late AD 1000s and early 1100s, we uncovered a gray pottery cooking vessel with a black-on-white bowl set upside down over the mouth of the jar, with a large potsherd covering a hole in the bottom of the bowl.  On top of all that were two bundles of split twigs, likely intended as basketry material (above).  The B/W bowl design (below) appears to have affinities with Ancestral Pueblo pottery from areas west of the Glen Canyon.  The big surprise was to find that the gray jar was filled with large flakes of salt.

In 2015, Sharyl Kinnear-Ferris and co-authors Winston Hurst and Kelly Hays-Gilpin, in the journal Kiva, addressed the question of how salt was moved around the prehistoric Southwest.  Their article described a remarkable cache of Hopi pottery vessels and gourd containers dating to the mid-1500s that had been left in a small natural shelter in what’s now Canyonlands National Park.  One of the pots was filled with salt, indicating that acquiring or trading salt was among the reasons for the approximately 150 mile trip from the Hopi mesas in Arizona to the Canyonlands Park region in Utah. A scientific collaborator, Dr. Antonio Simonetti, used inductively coupled plasma mass spectrometry (ICP-MS) to compare the trace elements in the Canyonlands salt with eight natural source samples and five other archaeological samples from around the Southwest (including from Benchmark Cave).

Several of the archaeological samples were generally similar to the main group of natural sources, but two–including the one from Benchmark Cave–were very different from one another and from the natural sources. The study didn’t tell us where the Benchmark Cave salt came from, but it showed the promise of additional future analyses to reveal how far people traveled to obtain salt and whether it was being traded. More work needs to be done!  Stay tuned!

The Bag of Cottonseeds

In the same stratum as the salt cache was a small leather bag crammed full of cottonseeds (below). The cotton fibers have been pulled off, suggesting that these seeds were likely intended for planting.  Noted archaeobotanist Karen Adams of Tucson has recognized that these seeds provide a rare opportunity to study the genetics of cotton domestication in the Southwest. Cotton-growing and production of cotton textiles was widespread in the later prehistoric periods in the parts of the Southwest that had long enough growing seasons and adequate water supplies. Cotton fabrics and weaving tools have been recovered from numerous sheltered sites, and archaeologists are beginning to recognize cotton pollen in probable field locations (see Smith and Gish 2015). The next frontier in cotton studies will be DNA analyses!

Adams has assembled a team of two molecular biologists, three archaeologists, and a Pueblo Indian weaver and grower of cotton. They plan to use DNA analysis to investigate varieties of cotton grown in recent times by Hopi farmers on the Colorado Plateau and Tohono O’odham farmers in the Sonoran Desert.  They will also analyze several prehistoric samples—one of 10 seeds from the Benchmark Cave cache, and three groups of seeds from different contexts in the Dyck Rockshelter in the Verde Valley of Arizona (Bostwick and Zoll 2015; Bostwick et al. 2015).  Comparison of genetic variation in the prehistoric and historic samples is expected to provide information about how Southwestern Indian farmers adapted native varieties of cotton to different growing conditions, and the extent to which present day varieties of Indian cotton are genetically similar to the prehistoric examples.

One of the first results of this project has been radiocarbon dating of cotton seeds from the two sites. The analyses, run by Aeon Laboratories in Tucson, indicate the Benchmark seed dates to between A.D. 1181 and 1222, and the date of the Dyck specimen most likely falls between A.D. 1050 and 1183 (Karen Adams, personal communication 2018).

This project described above is an initial pilot study.  Its larger goals are to develop a genetically-informed understanding of how Native Americans in several parts of the New World domesticated one or more species of wild cotton and created vibrant textile industries and trade networks.  I like to think that this little bag of cottonseeds from Benchmark Cave, excavated now 60 years ago, will soon make another significant contribution to this important story.

~Bill Lipe is professor emeritus of anthropology at Washington State University and a trustee of the Crow Canyon Archaeological Center, as well as a board Member of The Archaeological Conservancy.  He is a former president of the Society for American Archaeology (SAA), and in 2010, he received the Alfred Kidder Award from the American Anthropological Association (AAA).  He has done archaeological research in the Four Corners region of the Southwest since the late 1950s.

References for Further Reading

• Bostwick, Todd W., Charles E. Rozaire, and George Kritzman 2015. The 1962-1972 Excavations of the Dyck Rockshelter Along Wet Beaver Creek, Central Arizona: An Archival Reconstruction. Draft manuscript, on file at Verde Valley Archaeology Center, Camp Verde, Arizona.
• Bostwick, Todd and Ken Zoll 2015.  The Dyck Rockshelter. In The Dyck Rockshelter: An Exhibit of the Verde Valley Archaeology Center, 2015-2016, pp. 1-9.  Verde Valley Archaeology Center, Camp Verde, Arizona.
• Geib, Phil R. 1996.  AMS Dating of Plain Weave Sandals from the Central Colorado Plateau. Utah Archaeology 9(1):35-53
• Kinnear-Ferris, Sharyl, Winston Hurst, and Kelley Hays-Gilpin 2015. Hopi Pottery and Prehistoric Salt Procurement in Southern Utah Canyon Country. Kiva 80(3-4):250-280.
• Lipe, William D. 1960.  1958 Excavations, Glen Canyon Area.  University of Utah Anthropological Papers, No. 44. University of Utah Press, Salt Lake City.
• Smith, Susan J. and Jennifer W. Gish 2015. Archaeopalynology of PHX Sky Train Features. Chapter 7 in Hohokam Irrigation and Agriculture on the Western Margin of Pueblo Grande: Archaeology for the PHX Sky Train Project, edited by T. Kathleen Henderson, pp 157-172. Anthropological Paper No. 41, Archaeology Southwest, Tucson, Arizona.

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