Crop water availability in early agriculture: evidence from carbon isotopediscrimination of seeds from a tenth millennium BP site on the Euphrates

The analysis of carbon isotope discrimination (Delta) in crop plant remains from archaeological sites may help to assess water availability for early agriculture. This study presents the analysis of Delta in seeds of naked wh eat (Triticum aestivum/durum), lentil (Lens orientalis/ culinaris), and fla x (Linum sp.) found at the archaeological site of Tell Halula in the valley of the Middle Euphrates (Syria). This Neolithic site is the oldest in this region of the Fertile Crescent where the cultivation of domesticated plant s has been reported, with seed remains ranging from 9550 to 8465 sp. Most o f the seeds analysed showed Delta values greater than 16 parts per thousand , reaching 20 parts per thousand for some samples of flax. For wheat, Delta values were much higher than those reported in present-day (1996) durum wh eat crops cultivated under rainfed conditions in north-west Syria under env ironments with somewhat higher rainfall than Tell Halula. Similarly, grains of present-day (1997) barley cultivated in the archaeological site also sh owed lower values than those found in archaeological kernels. An empirical relationship between Delta of mature kernels and total precipitation (plus irrigation where applicable) from heading to maturity (r(2) = 0.82, n = 11) was established for durum wheat, currently cultivated in different environ ments of the Mediterranean basin. The resulting relationship was applied to the data on Delta of wheat fossil kernels from Tell Halula to estimate the accumulated water inputs during the time (about 6 weeks) the kernels were produced. Calculated water inputs for wheat during early agriculture were l over 110 mm) at least 5 times higher than current-day rainfall accumulated in Tell Halula during the same phenological period. These results strongly suggest that early agriculture wheat was cultivated at Tell Halula under mu ch wetter conditions than are currently to be found in the area. The presen ce of flax and its very high Delta values also support this conclusion. Whe ther such humid conditions during cultivation were due to moister condition s prevailing at this time, by planting in alluvial areas or by irrigation w orks is discussed.