Isotope evidence for agricultural extensification reveals how the world's first cities were fed

Abstract

This study sheds light on the agricultural economy that underpinned the emergence of the first urban centres in northern Mesopotamia. Using δ13C and δ15N values of crop remains from the sites of Tell Sabi Abyad, Tell Zeidan, Hamoukar, Tell Brak and Tell Leilan (6500–2000 cal bc), we reveal that labour-intensive practices such as manuring/middening and water management formed an integral part of the agricultural strategy from the seventh millennium bc. Increased agricultural production to support growing urban populations was achieved by cultivation of larger areas of land, entailing lower manure/midden inputs per unit area—extensification. Our findings paint a nuanced picture of the role of agricultural production in new forms of political centralization. The shift towards lower-input farming most plausibly developed gradually at a household level, but the increased importance of land-based wealth constituted a key potential source of political power, providing the possibility for greater bureaucratic control and contributing to the wider societal changes that accompanied urbanization.

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Figure 1: Geographical location of the study area.
Figure 2: Modern cereal grain δ15N values plotted against the natural log of mean annual rainfall, colour coded by manuring level.
Figure 3: Archaeological cereal grain sample δ15N values plotted against date.
Figure 4: The probability of an archaeological cereal grain sample having a manuring level m or lower plotted against site size.
Figure 5: Archaeological cereal grain and pulse sample Δ13C values plotted against date.
Figure 6: Human and faunal bone collagen and crop δ13C and δ15N values plotted in relation to ellipses representing the expected distributions (mean ± 2 s.d.) of δ13C and δ15N values of individuals consuming various dietary combinations of cereal grains, pulses and animal products (milk and/or meat).

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Acknowledgements

The work reported here was funded by the European Research Council (AGRICURB project, grant no. 312785, A.B.) and the Natural Environment Research Council (NERC standard grant NE/E003761/1, A.B.). A portion of the human isotope data from Tell Brak has been obtained with the financial support by the Polish National Science Centre, grant No. 2012/06/M/HS3/00272. Archaeobotanical analyses at Tell Sabi Abyad were funded by the ‘Consolidating Empire’ project at Leiden University (ERC Starting Grant, no. 282785, PI Düring). Archaeobotanical analyses at Tell Leilan and Tell Zeidan were funded by an NSF Early Faculty CAREER Award (1054938) granted to A.Sm. We are grateful to C. Montrieux and E. Wilman for processing archaeobotanical samples and faunal bone collagen for isotope analysis.

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Authors

Contributions

A.B. conceived the study and contributed to data interpretation and the writing of the manuscript; A.K.S. designed the sampling protocol, carried out analyses, analysed the data and wrote the paper with A.B.; M.C., F.F., M.M.H. and A.Sm. contributed botanical material and data; A.M., G.S. and H.W. contributed data and gave permission for analysis of material; R.M., A.K.P. and J.A.W. contributed faunal material and data; G.K.N. led the statistical analysis and developed the statistical models; M.C.P. and A.So. contributed human bone and dentine material and data. All authors discussed the results and implications and commented on the manuscript at all stages.

Corresponding author

Correspondence to Amy K. Styring.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Statistical supplement. Describes the statistical analyses carried out on the δ15N values of archaeological cereal grains and refers to data in Supplementary Data 1 and 2 and Supplementary Code 1–16. (PDF 1780 kb)

Supplementary Figure 1

Fourier transform infrared spectra of an archaeological pea seed sample contaminated with 50% carbonate by dry mass (a); an archaeological pea seed sample contaminated with 5% carbonate by dry mass (b); an archaeological six-hulled barley grain sample from Tell Brak (TBR108), showing evidence for approx. 5% carbonate contamination by dry mass (c); and an archaeological hulled barley grain 8 sample from Tell Zeidan (TZD03), showing no evidence of carbonate contamination (d). Peaks at wavelengths of 720 cm−1 and 870 cm−1 are characteristic of carbonates found in soil and are therefore indicative of potential contamination. (PDF 191 kb)

Supplementary Table 1

Carbonized cereal grain and pulse seed δ13C and δ15N values from: Tell Sabi Abyad, Tell Zeidan, Hamoukar, Tell Brak and Tell Leilan. (XLSX 128 kb)

Supplementary Table 2

Faunal and human bone collagen δ13C and δ15N values from: Tell Brak (and nearby Chagar Bazar) and Tell Leilan. (XLSX 64 kb)

Supplementary Data 1

Metadata and δ13C and δ15N values of carbonized cereal grains from archaeological sites used in statistical analyses. The ID of each sample matches the SampleID in SI20. The variables are explained in SI1. (CSV 34 kb)

Supplementary Data 2

Metadata and δ13C and δ15N values of uncarbonized cereal grains from modern farming regimes used in statistical analyses. The variables are explained in SI1 (statistical supplement). (CSV 25 kb)

Supplementary Code 1

SI4_MAIN_FILE_START_HERE. R script used in statistical analysis of archaeological cereal grains. Start statistical analysis here. (TXT 25 kb)

Supplementary Code 2

SI5_LoadData. R script used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (TXT 1 kb)

Supplementary Code 3

SI6_PriorsAndLikelihoods. R script used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (TXT 6 kb)

Supplementary Code 4

SI7_SimpleImpute. R script used in statistical analysis of archaeological cereal grains. This is referred to in Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (TXT 8 kb)

Supplementary Code 5

SI8_SingleImputation. R script used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (TXT 1 kb)

Supplementary Code 6

SI9_xvalSI. R script used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (TXT 2 kb)

Supplementary Code 7

SI10_NLM-NORE-NOM_RESout1. R data used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (ZIP 15063 kb)

Supplementary Code 8

SI11_NLM-NORE-PO_RESout1. R data used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (ZIP 15083 kb)

Supplementary Code 9

SI12_NLM-RES-PO_RESout3. R data used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (ZIP 11646 kb)

Supplementary Code 10

SI13_NLM-RES-NOM_RESout2. R data used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (ZIP 11734 kb)

Supplementary Code 11

SI14_CleanMCMCoutput. R script used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (TXT 2 kb)

Supplementary Code 12

SI15_NLM-ALLRE-PO-NORES-SYNout. R data used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (ZIP 1396 kb)

Supplementary Code 13

SI16_NLM-RES-PO-NORES-SYNout. R data used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (ZIP 1296 kb)

Supplementary Code 14

SI17_NLM-NORE-PO-NORES-SYNout. R data used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (ZIP 1448 kb)

Supplementary Code 15

SI18_NLM-RES-NOM_RESout1000. R data used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (ZIP 11517 kb)

Supplementary Code 16

SI19_NLM-RES-NOM_RESout10. R data used in statistical analysis of archaeological cereal grains. This is loaded from Supplementary Code 1 (SI4_MAIN_FILE_START_HERE). (ZIP 11511 kb)

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Styring, A., Charles, M., Fantone, F. et al. Isotope evidence for agricultural extensification reveals how the world's first cities were fed. Nature Plants 3, 17076 (2017). https://doi.org/10.1038/nplants.2017.76

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