Fig 1.
Contextual information for maize and faunal isotopic data.
(A) Map of Peruvian guano islands [11] and Chincha and Chile [10] study areas, which yielded maize isotopic data that are compared in this study. (B) Map of Chincha study area, with middle valley cemeteries sampled for maize (marked by pink circles), the site of Jahuay (marked by white triangle) sampled for faunal remains, and the Chincha Islands (marked by the dotted white line). Shaded relief and country borders (A) are from Natural Earth. Sentinel-2 satellite imagery (B) was freely downloaded from https://dataspace.copernicus.eu/.
Fig 2.
The primary guano-producing bird species.
(A) Sula variegata (Peruvian booby). (B) Pelecanus thagus (Peruvian pelican). (C) Leucocarbo bougainvilliorum (Guanay cormorant). Photos by Diego H. (A and C) and Claude Kolwelter (B), iNaturalist.org. Licensed under CC-BY 4.0. Cropped from originals.
Fig 3.
LIP and LH seabird imagery from the Peruvian southern coast.
(A) Ceremonial digging stick or paddle, The Met Museum 1979.206.1025. (B) Bone balance-beam scale, The Art Institute of Chicago 1955.2579d. (C) Adobe frieze (now destroyed) at the site of La Centinela c.1938, Bennett Greig (1907–1944). (D) Embossed lead and silver ball depicting seabirds eating a fish, The Met Museum 82.1.22. (E) Ceramic jar from UC-018 mortuary site, middle Chincha Valley, photo by J. Bongers. (F) Pyro-engraved gourd from Jahuay, Quebrada de Topará, photo by J. Osborn. (G) Embroidered textile from UC-25, middle Chincha Valley, photo by C. O’Shea. (A-D): CC0 Public Domain. All photos cropped from the originals.
Fig 4.
Comparison of δ13C and δ15N of archaeological maize from Chincha and Chile [10].
Scatterplot of δ13C and δ15N with a convex hull constructed for the range of Chincha samples (A) and box-and-whisker plots of δ13C (B) and δ15N values (C) organized by period (ND = no date/maize from undated context).
Fig 5.
Isotope space size and overlaps.
Plotted isotope space kernel utilization density functions (KUD; top row) and standard ellipse areas (SEA; bottom row) comparing Chincha maize with maize grown under different experimental fertilizer conditions [16]. Columns display results at commonly selected contour levels – 75% and 95%.
Fig 6.
Basic schematic of how marine “contaminated” plants can create equifinality issues for paleodietary interpretations.
The plot compares Chincha maize (C4 crops) artificially enriched in 15N and with the isotopic measurements from archaeological guano birds (this study), demonstrating the potential utility of δ34S for discriminating between terrestrial plants with marine products and marine resources. (A) δ13C and δ15N data with boxes for expected terrestrial C4 and C3, freshwater, and marine ranges [53]. (B) δ34S and δ15N data with boxes for expected freshwater and marine ranges indicated [47].