9,000-year-old barley consumption in the foothills of central Asia

Abstract

Scholars are increasingly favoring models for the origins of agriculture that involve a protracted process of increasing interdependence within a series of mutualistic relationships between humans and plants, as opposed to a rapid single event or innovation. Nonetheless, these scholars continue to debate over when people first started foraging for grass seeds, when they began to readily utilize sickles, how prominent the early selection pressures were, and when the first traits of domestication fully introgressed into the cultivated grass population. Here, we present complementary archaeobotanical and archaeological (stone tool) evidence for cereal foragers from Toda-1 Cave in the Surkhan Darya, dating to 9200 cal BP. We conclude that early Holocene foragers were processing grains along with nuts and fruits as far north as the rich river valleys of southern Uzbekistan. These data expand the known range that preagricultural cereal foragers covered in the early Holocene, adding to our understanding of the cultural processes that led to farming. Additionally, we present the earliest evidence for people interacting with the progenitors for pistachios and apples (or a close apple relative). The complex foraging behaviors that led to cultivation were being undertaken by people during the early Holocene across a wider area of Eurasia than previously thought.

Keywords: agriculture origins; barley; central Asia; climate change; holocene.

Fig. 1.

Location, culture layer distribution, and chronostratigraphy of Toda-1 Cave. (A) Location of Toda-1 Cave and topography of Amu Darya Valley. (B) External photo of Toda-1 Cave (by Xinying Zhou). (C). Cross section and stratigraphic layers of Toda-1 Cave. (D) The culture layer group and sublayer with radiocarbon data of Section-1 of T5, Toda-1 Cave.

Fig. 2.

Stone tools from early Holocene layers of Toda-1 Cave: 1-3,7. Tabular anvil with pitting (T5-L18, ca. 8000 cal BP); 4. Hammer stone with pitting T5-L17, ca. 7800 cal BP); 5 to 6. Retouched flakes (T5-L18, ca. 8000 cal BP); 8. Polished adze (T5-L18, ca. 8000 cal BP); 9. Grinding stone (T5-L18, ca. 8000 cal BP); 10. Pebble axe (T5-L17, 7800 cal BP); 11 to 13. Microblades with continuous edge damage (T5-L-24, ca. 9000 cal BP); 14 to 17. Microblades with partial edge damage (T5-L18, ca. 8000 cal BP); 18. Blade (T5-L-24, ca. 9000 cal BP); 19 to 24 Microblades with partial edge damage (T5-L-23, ca. 8800 cal BP); 25. Blade with partial edge damage (T5-L23, ca. 8800 cal BP); (Scale bar, 1 cm.)

Fig. 3.

CT (computed tomography) photo of carbonized seeds from Toda-1 Cave (Scale bar, 1 mm.): 1-7, barley grains: 1. T5-L21, ca. 9000 cal BP; 2. T5-L21, ca. 9000 cal BP; 3. T5-L19, ca. 8000 cal BP; 4. T5-L21, ca. 9000 cal BP; 5. T5-L19, ca. 8000 cal BP; 6. T5-L19, ca. 8000 cal BP; 7. 22B, ca. 9000 cal BP; 8. Trigonella (T5-L23, ca. 9000 cal BP); 9. Piptatherum; T5-L19, ca. 8000 cal BP; 10. and 11. Malus/Pyrus (T5-L18, ca. 8000 cal BP).

Fig. 4.

The best-preserved representative specimens from Toda-1 Cave, breadth, and thickness measurements, compared to early southwest Asian assemblages (data from2,20,51,52). The Toda-1 Cave barley plots well within the wild range.

Fig. 5.

Comparison of the environmental index of Toda-1 Cave and climate change records: (A) the vegetation (pollen), grazing intensity (δ¹⁵N) change record from Toda-1 Cave T5; (B–D) pollen percentage in Toda-1 Cave sediments from T5: (B) Chenopodioideae; (C) Poaceae; (D) Quercus; (E) first presence of plant and animal remains in Toda-1 Cave, foxtail millet (Setaria italica), grape (Vitis vinifera), apple relative (Malus/Pyrus), Russian olive (Elaeagnus sp.), Pistachio (Pistacia vera), barley (Hordeum vulgare ssp. spontaneum); (F) the summer solar isolation intensity change at 60 °N; (G) the precipitation change record by δ¹⁸O of Jeita Cave, Levant region (48); (H) the India monsoon intensity change record by δ¹⁸O of Qunf Cave, Oman (49); (I) middle Asia drought index record by Talisman cave, Fergana, Kyrgyzstan (50); (J) arid events recorded by element Ti concentration of Neor peat, northwestern Iran; (K) radiocarbon data (n = 29) possibility distribution of Toda-1 Cave using IntCal20 atmospheric curve (51).

Fig. 6.

The diffusion route and the timeline of cereal foragers from west Asia to east. (A) Near East, Iran, central Asia, South Asia early Neolithic site and Toda-1 Cave site distribution. (B) The diffusion timeline of foragers indicated by the age span bar of the numbered sites, the dashed bar represents estimated ages, marked with evidence of wild/domesticated cereal and domesticated animals of the regions (detail of the sites see Dataset S1).