Strontium isotope evidence for Pre-Islamic cotton cultivation in Arabia

With a view to understanding the dynamics of ancient trade and agrobiodiversity, archaeobotanical remains provide a means of tracing the trajectories of certain agricultural commodities. A prime example is cotton in Arabia, a plant that is non-native but has been found in raw seed and processed textile form at Hegra and Dadan, in the region of al-‘Ulā, north-western Saudi Arabia (Fig. 1) – sites of critical importance given their role in the trans-Arabian trading routes during Antiquity.

Fig. 1. Geological map of the study area with strontium isotope values of sampled plants [USGS basemap (Brown et al., 1963) https://pubs.er.usgs.gov/publication/i204A]. Green-outlined sites = wadi Q27 al-‘Ulā, immediately surrounding Hegra/Dadan. All sites = regional.

Here, we demonstrate that the measurement of strontium isotopes from precleaned archaeological cotton is methodologically sound and is an informative addition to the study of ancient plant/textile provenance, in this case, putting forward evidence for local production of cotton in oasis agrosystems and possible external supply (Fig. 2).

Fig. 2. Comparative of Sr isotopes of modern plants, archaeological non-cotton plants (barley grain, date palm seed and charcoal, tamarisk charcoal, Amaranthaceae charcoal), cotton seeds, cotton textiles and groundwater. Circles indicate boxplot outliers.

The presence of locally-grown cotton at these sites from the late 1st c. BCE–mid 6th c. CE is significant as it demonstrates that cotton cultivation in Arabia was a Pre-Islamic socio-technical feat, while imported cotton highlights the dynamism of trade at that time (Fig 3.).

Fig. 3. Sr isotope values of modern bio-available plant material, categorised based on the geological unit on which they grew. Open circles = local (Site of Hegra/Dadan and wadi al-‘Ulā), all circles = regional.

Reference: Saskia Ryan, E. Douville, A. Dapoigny, P. Deschamps, V. Battesti, A. Guihou, M. Lebon, J. Rohmer, V. Dabrowski, P. Dal Prà, L. Nehmé, A. Zazzo, C. Bouchaud., 2023. Front. Earth Sci., Sec. Quat. Sci., Geomor. & Paleoenviron., 2023, 11:1257482., DOI : 10.3389/feart.2023.1257482