DOI: 10.5061/dryad.vx0k6dk3c
title: Ancient use of the four corners potato

description: Despite its long history, utilitarian value, and cultural significance to
 several Indigenous Tribes in the Southwest USA, the extent to which the
 Four Corners potato (Solanum jamesii Torr.) has been domesticated requires
 circumscription. Establishing the temporal and spatial dimensions of
 intentional cultivation would provide an essential component of the
 domestication argument. This project tests the hypothesis that S. jamesii
 tubers were processed with ground stone tools from archaeological sites
 located beyond the natural range of the species, especially where genetic
 evidence has previously indicated human transport and establishment in
 gardens. Microbotanical evidence, in the form of starch granules from 401
 ground stone tools at 14 archaeological sites, is examined. More than
 6,500 starch granules were recovered from the tools; 163 of which were
 assigned to S. jamesii.  Four sites (North Creek Shelter, Long
 House/Mesa Verde, Pueblo Bonito/Chaco Canyon, and Point of Pines) show
 consistent use of S. jamesii (ubiquity &gt;18%), as early as 10,900
 cal BP, and well into Puebloan times.  Three of these sites are
 located far north of the species’ center of distribution in the Mogollon
 region, across hundreds of kilometers of the Colorado Plateau, and still
 support an extant population nearby. This suggests an anthropogenic
 distribution of S. jamesii across the Four Corners region and a unique
 cultural identity around the use of this native potato.  These
 findings, combined with ethnographic interviews and nutritional data,
 provide clear evidence of use in relation to natural and anthropogenic
 distributions, thereby allowing an assessment of the degree to which these
 energy-rich, nutritious, and compact tubers were purposely used and
 transported.
description: <strong>Sites and Tools</strong>
 There are many archaeological sites within and beyond the
 documented range of <em>S. jamesii</em>. Relatively few have
 been excavated, and fewer still have ground stone tools from buried
 deposits with published contextual details. Only excavated and recorded
 sites that had available ground stone tools would be suitable for starch
 granule analysis.  Fortunately, eight repositories had collections from 14
 sites that met these criteria and provided a wide temporal range (early
 Holocene through Protohistoric) for sampling a sufficient number of
 properly stored tools. Inventories of ground stone
 tools (i.e., manos and metates) from the 14 sites were examined to
 determine the availability and feasibility for sampling. Objects were not
 chosen if they 1) were on exhibit, 2) had an unknown location at the
 repository, 3) were not collected, or 4) were restricted objects.
 Approximately 98% of the ground stone tools sampled contain site and/or
 stratigraphic provenience. Furthermore, information regarding curation
 practices (i.e., handling, cleaning, and storage) was considered so that
 the probability of cross-contamination was low (i.e., objects bagged
 individually, stored in sealed boxes vs. open shelves, etc.). A total of
 401 ground stone tools from eight repositories (American Museum of Natural
 History, Arizona State Museum, Brigham Young University Museum of Peoples
 and Cultures, Edge of the Cedars, Mesa Verde Visitor and Research Center,
 Museum of Northern Arizona, Natural History Museum of Utah, and the
 Western Archaeological Conservation Center) were ultimately sampled for
 starch granule analysis. <strong>Starch Granule
 Analysis</strong> Starch granules are microscopic
 plant structures formed from photosynthates by subcellular amyloplasts as
 energy reserves. Long-term energy reserves, or “storage starches,” are
 most abundant in seeds, fruits, and underground storage organs (USOs -
 corms, tubers, taproots, etc.). These starch granules are released from
 cells during food processing and can subsequently become deposited in the
 cracks and crevices of archaeological tools. Because of their
 microcrystalline structure, starch granules are relatively resistant to
 organic decay and are often preserved for millennia in archaeological
 contexts. Consumable supplies used in this study, such
 as nitrile gloves, weigh boats, toothbrush heads, and test tubes, were
 only used once to prevent cross-contamination during sampling and
 processing.  Extraction of starch granules began with placing a portion of
 each ground stone tool in a weigh boat filled with deionized water
 (diH20), which was then placed in a sonicator. Stones that were too large
 to fit in the sonicator were spot sampled with a sonicating toothbrush.
 Spot sampling uses a smaller surface area than sonication, so starch yield
 may be affected. Each sample was then filtered with diH20 using a 125 µm 
 U.S.A. standard test sieve and transferred to a 50 ml sterile test tube.
 Samples were centrifuged for three minutes at 3000 RPM. The supernatant
 was discarded, and the re-suspended sample pellet was transferred to a 15
 ml sterile test tube. Heavy liquid was used to isolate
 starch granules from the samples; 5 ml of lithium heteropolytungstate (LST
 - specific gravity 2.00 - 2.35) (Central Chemical Consulting, Malaga,
 Australia) was added to each sample and resuspended with a vortex mixer.
 The sample was then centrifuged for 15 minutes at 1000 RPM. The suspended
 fraction was decanted into another sterile set of labeled test tubes. Two
 more rinses (addition of diH20 and centrifugation, three minutes at 3000
 RPM) removed any residual heavy liquid. Acetone was added, then each
 sample was spun and allowed to dry overnight. This process resulted in the
 formation of a small pellet of organic material that would include starch
 granules, if present. <strong>Starch Granule
 Identification</strong> Following processing,
 pellets were re-suspended in a few drops of a 50/50 glycerol and diH2O
 solution and then mounted on a glass slide. Each slide was scanned in its
 entirety using a transmitted brightfield microscope fitted with polarizing
 filters and Nomarski optics (Zeiss Axioscope 2, Zeiss International,
 Göttingen, Germany). A digital camera (Zeiss Axiocam HRc) with imaging and
 measurement software (Zen Core v2.7) was used to capture images and to
 make starch granule measurements. Because ground stone tools were made
 available from repositories over six years, imaging and measurements were
 performed by multiple collaborators. Consistency was assured by frequent
 training and assigning each collaborator to all tools from a single
 site. Previous studies discuss our approach for
 identifying <em>S. jamesii</em> starch granules. Those studies
 developed a set of statistically defined diagnostic characteristics that
 include: 1) possession of an eccentric hilum, 2) the presence of a
 longitudinal fissure, 3) the absence of fissure branching, 4) a ratio of
 fissure width to granule width in the range of 0.21–0.28 (mean ratio ± 99%
 CI), and 5) mean maximum granule length greater than 34.88 μm (mean minus
 the 99% CI). Archaeological granules that have an eccentric hilum and
 possess two or more of the characteristics are taxonomically assigned to
 <em>S. jamesii</em>. Granules with eccentric hilum and
 possessing less than two of the characteristics could be <em>S.
 jamesii,</em> but could also belong to other plant taxa with USOs
 (e.g., Liliaceae) and in this study, remain unidentified.
 <strong>Control Samples</strong>
 Starch occurs naturally on laboratory surfaces and can be
 airborne, so precautions were taken to minimize contamination during
 laboratory processing. Passive traps were placed in the NHMU laboratory
 spaces and collections room and left in place for approximately one week
 during sample processing.  In addition to passive
 traps, control samples were taken from feature fill sediments and/or
 animal bones to detect background levels of starch at four archaeological
 sites.  Sediment control samples from North Creek Shelter were processed
 and analyzed in 2013. However, subsequent research has shown that
 sediments may not be ideal control samples due to the natural occurrence
 of starch and enzymatic damage caused by soil bacteria. Therefore, we
 sampled animal bones from the same cultural deposits where ground stone
 tools were recovered at Danger Cave, Camel's Back Cave, and Sudden
 Shelter. Not all archaeological sites had sediment or
 faunal bones available for sampling, as many collections were curated
 decades ago, before the routine practice of collecting associated sediment
 during excavation. Moreover, submitting additional research requests to
 sample sediment or faunal material from curated collections was not always
 feasible. Although feature fill sediments and animal bones located in situ
 near artifacts may have been exposed to starch from the processing of
 associated plant materials, the quantity of starch granules from such
 sources is expected to be minimal compared to starch granules embedded in
 the cracks and crevices of ground stone tools.
 <em>Interviews with elderly people</em>: The elder
 interviews were recorded, transcribed, and are archived at Utah Diné
 Bikéya, where the identities of the elders are held incognito. Before the
 start of our project, we submitted an application to the University of
 Utah Institutional Review Board (IRB), and that approval letter
 (IRB_00112805) is attached to the article submission.
description: # Ancient use of the four corners potato Dataset DOI:
 [10.5061/dryad.vx0k6dk3c](10.5061/dryad.vx0k6dk3c) ## Description of the
 data and file structure ### Files and variables #### File: S1_Table.xlsx
 **Description:** Site name, repository, catalog number, lab specimen
 number, and provenience of each ground stone tool analyzed for starch.
 #### File: S2_Table.xlsx **Description:** Lengths and morphological
 characters were measured and documented on each starch granule from all
 ground stone tools (n=401) analyzed in this study. Each tab contains
 starch granule data from an archaeological site (n=14). All starch
 granules have length measurements, but not all morphological characters
 were documented on all granules. ##### Variables: * Granule Length (µm =
 microns), Shape, Hilum position, Cavity, Cross, Fissures, Lamellae,
 Pressure Facets. Numbers in the cells are the measured length or the
 presence (1) or absence (0) of that specific variable. * Missing values or
 'n/a' indicate no measurements were made. #### File:
 S3_Table.xlsx **Description:** Taxonomic assignment of granules to S.
 jamesii is based on the possession of an eccentric hilum and two or more
 diagnostic characters. ##### Variables: * Granule Length (µm = microns),
 Eccentric Hilum (yes/no), Longitudinal Fissure (yes/no), Branched Fissure
 (yes/no), Fissure Ratio (width of fissure/width of granule). * Missing
 values or 'n/a' indicate no measurements were made. ## Access
 information Other publicly accessible locations of the data: * None Data
 was derived from the following sources: * None