Fig 1.
This map was made in ArcGIS software with original materials as well as open access files obtained from China historical GIS database at Harvard University—http://sites.fas.harvard.edu/~chgis/.
Fig 2.
A selection of ma’an style vessels from the Zhanqi cemetery.
Fig 3.
Observed use-wear patterns on Siwa ma’an cooking vessels.
A. Frontal image of ma’an jar showing external soot pattern (base is about 4.5 cm across). B. Handle-sided view of ma’an jar showing external soot pattern. C. Changes in paste color resulting from fire clouding or other production processes. D. Internal carbonization on upper portion of lip. E. Internal carbonization on walls. F. Ma’an jar with use-wear pattern (soot and oxidation).
Fig 4.
Schematic image of dominant use-wear pattern observed on Siwa ma’an cooking vessels.
Fig 5.
Use-wear alteration marks of Zhanqi li vessels.
A. Soot remains extending from the belly down to the foot. B. Soot remains on the handle perpendicular to the side exposed to the fire. C. Heavy sooting on the base and oxidation on the feet (nipple), indicating placement base side down in the fire. D. Heavy carbonization can be seen in each of the tripod’s three feet, an expected outcome of a cooking vessel placed in the fire or exposed to a fire source base side down from which enough liquid evaporated to allow food particles to burn and char.
Fig 6.
Schematic image of dominant use-wear pattern observed on Siwa li cooking vessels.
Fig 7.
Possible positions that could have generated the dominant use-wear pattern observed on Siwa ma’an cooking vessels.
Option 1: commonly understood use position for cooking vessels (it is possible that the vessel was exposed to a heat source on its sides). Option 2: more likely position given the lack of use-wear observed internally on the base of vessels.
Table 1.
Use-wear remains on Zhanqi ceramics.
Fig 8.
Use-alteration marks (chipping—left) and heavy soot (exposure to fire—right) on ma’an vessels.
Table 2.
Results of organic residue analysis of ten pottery sherds from the Zhanqi cemetery in China’s Gansu Province.
Fig 9.
Plot of carbon to nitrogen ratios and δ15N obtained on charred deposits (foodcrusts) of Siwa pottery from the Zhanqi site, against archaeological bone collagen reference data from China (see S1 File, Table 1).
The collagen δ15N values were adjusted by +2‰ to correct for the collagen to tissue offset in order to make these values more comparable with the foodcrusts [51].
Fig 10.
Partial gas chromatograms of lipid extract M51-1-F obtained by direct acid-catalyzed transesterification (for more details see S1 File).
A. Partial chromatogram obtained with a DB5-ms (5%-phenyl)-methyl polysiloxane column: Cn:x are fatty acids with carbon length n and number of unsaturations x; br are branched-chain acids; IS are the internal standards (n-tetratriacontane and n-hexatriacontane). The insert shows peaks corresponding to miliacin (olean-18-en-3β-ol methyl ether), a plant biomarker enriched in grains of broomcorn millet (Panicum miliaceum) and stigmastanol, another plant biomarker identified. To monitor the retention time and confirm the presence of miliacin, an authentic standard of miliacin was injected in the same GCMS run. B. Partial SIM chromatogram (m/z 105 ion) obtained with a DB23 (50%-Cyanopropyl)-methylpolysiloxane column shows the distribution of ω-(o-alkylphenyl)alkanoic acids with 18 carbon atoms (letters from A to I corresponding to the isomers).
Fig 11.
Boxplots of E/H ratio of modern references thermally degraded in the laboratory [57] and Siwa archaeological samples.
Plots represent median (solid line), mean (dashed line), ranges and quartiles. The arrow (thermal impact) shows the effect of increasing temperature on the E/H ratio.
Fig 12.
Compound specific stable carbon isotopic data from Siwa potsherds compared with reference fats and oils and illustration of potential mixtures.
In each plot the δ13C16:0 values are plotted against Δ13C (δ13C18:0 - δ13C16:0) to distinguish the different sources of fats. A. Fatty acids carbon stable isotope values plotted against reference ranges. The ranges represent the mean ± 1 s.d. of the Δ13C values for a global database comprising modern reference animal fats raised on a variety of C-3 and mixed C3/C4 diets [69] B. Shows average isotopic endpoints for non-ruminant (NR), ruminant adipose (RA), and ruminant dairy (RD) fats with C3 and mixed C3/C4 diets and millet obtained from measurements of authentic modern products corrected for post-industrial carbon (S1 File, Table 2). Hypothetical mixing lines in 10% increments are shown between each endpoint and millet calculated from the mean relative amount of each fatty acids in each product using data obtained from the USDA database.