Paleolithic humans subsisted mainly on small- to medium-size hoofed animals. Scientists have surmised that these early hunters must have eventually expanded their food repertoire in order to sustain a growing population, but exactly when they began turning to plants for fuel was unknown. In the new work, Ehud Weiss of Harvard University and his colleagues analyzed plant remains from an archaeological site in Israel called Ohalo II, which dates to 23,000 years ago and includes several huts, hearths and a human grave. Upon excavation, the locality yielded more than 90,000 specimens from 142 plant taxa, including 19,000 well-preserved grass grains. The authors note that the finds not only provide evidence for broad spectrum plant collecting, but also push back the evidence for significant grass collecting 10,000 years earlier than previously had been known. Among the ruins were pieces of acorns, almonds, pistachios, wheat, barley, berries, figs and grapes.
Some of the foods were short-lived menu preferences, however. Remains from other sites suggest that by 8,000 years ago, most of the small-grained wild grasses uncovered at Ohalo II were no longer part of the ancient food pyramid. Instead, early humans favored the larger-grained cereal crops, the domestication of which led to the rise of modern agriculture. The researchers describe their discovery in a report published online today by the Proceedings of the National Academy of Sciences.