Stone blades yield early cultivation clues.

Stone blades yield early cultivation clues

Scientists have long speculated about the uses of stone-bladed sickles found at prehistoric sites in the Middle East. Microscopic analysis of polish and wear on a large sample of the stone blades now indicates they were used to harvest cereals for food between 12,000 and 6,000 years ago, according to a report in the February CURRENT ANTHROPOLOGY.

"It also appears some kind of small-scale cultivation of cereals involving digging in the soil took place 12,000 years ago," says archaeologist Romana Unger-Hamilton of University College in London, England.

If the latter conclusion holds true, a 3,000-year span separated early cultivation efforts and the appearance of full-scale agriculture in the same region. This supports other recent evidence that agriculture originated in a step-by-step process, not a sudden revolution.

Unger-Hamilton's first step was to produce 295 experimental blades from a variety of stone, including material from near the archaeological sites. The blades were used, either bare-handed or attached to copies of bone and wooden handles discovered with the prehistoric blades, to harvest 17 wild and 12 cultivated plant species, as well as 5 types of weeds growing among the plants. Harvesting was done as close as possible to archaeological sites.

A polish develops on the blades with continued cutting of plants, Unger-Hamilton says. When viewed under a microscope, polish distribution clearly differs among the three plant groups studied; in most cases, it differs from one plant species to another. Blade polish variations also indicate whether a plant was cut under the seed or near the base, whether it was green or ripe, wet or dry at the time of cutting, whether the blades were attached to a handle and whether the handle was curved or straight.

When plants are cut close to the ground, and the soil is loose, striations or grooves appear in the blades, Unger-Hamilton adds.

Her next step was to study the polish on 761 flint sickle-blades collected at pre-historic sites in present-day Israel. Some blades date back to the Natufian culture, which existed between 12,000 and 10,000 years ago. Others came from Neolithic, or New Stone Age, locations dating to between 10,000 and 8,000 years ago.

About 80 percent of the blades had a polish distribution similar to experimental cereal polishes, Unger-Hamilton says. The overall pattern suggests most blades were attached to curved sickles, she notes.

About one-quarter of the Natufian and three-quarters of the Neolithic blades were heavily striated. The steady increase in striations over time and their consistent distribution among the early sites indicates, in Unger-Hamilton's view, the harvesting of cereals from tilled soil occurred 12,000 years ago and gradually became more commonplace.

In her harvesting work with the experimental blades, conducted in 1985 and 1987, Unger-Hamilton observed dramatic variations in the availability of wild cereals and other wild plants. Wild emmer and barley near the older archaeological sites ripen quickly and are available for harvesting for only a few days before local hot winds shatter the plants' protective ears. Plant food shortages may have provided an important incentive for cereal cultivation by early Natufians, Unger-Hamilton says.

Other factors, such as the appearance of village settlements and population pressures, may not have played crucial roles in stimulating Natufian plant cultivation, she maintains. But a warming of the climate around 12,000 years ago appears to have contributed to cereal availability and the potential for cultivation.

Unger-Hamilton's demonstration of cereal cutting by early Natufians is persuasive, says Harvard University archaeologist Ofer Bar-Yosef, but it is not clear whether they tilled the soil or harvested cereals in large natural stands. It is difficult to establish whether wild or cultivated plants were gathered, he notes, since soils in that region do not contain many fossilized plant remains.

About 50 years ago, Bar-Yosef says, archaeologists first suggested the sickle-blades were used to cut edible plants.

Bar-Yosef asserts an abrupt climatic warming, combined with increasing populations in areas where resources had not been overexploited, sparked early Natufian plant cultivation.