STONE-AGE foragers gathered small grass seeds before they began cultivating larger cereal grains, an excavation of an Israeli site shows. The discovery fills in a crucial gap in the development of agriculture.
Bones preserved at ancient campsites allow archaeologists to trace changes in the meat composition of stone-age diets. Excavations of 50,000-year-old sites indicate that people initially ate small to medium hoofed mammals, like goats or sheep, then turned to other small mammals, birds and fish as food resources grew short. But plants preserve less well, making it difficult to document their use before about 12,000 years ago.
Now nearly 19,000 well-preserved grass seeds have been found at the Ohalo II site on the Sea of Galilee dating back 23,000 years, giving researchers an opportunity to study a little-known period of prehistory. Over 16,000 seeds came from small-grained grasses such as brome, and only 2600 from wild cereals.
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That means diets based on a broad range of grains evolved some 10,000 years earlier than had been recognised, says Ehud Weiss of Harvard University (Proceedings of the National Academy of Sciences, DOI/10.1073/pnas.0402362101). The small-grained grass seeds faded from the diet between 12,500 and 8000 years ago as people turned to cultivating larger cereal grains that yielded more food value for less effort.