Scientists have discovered the oldest evidence of purposeful harvesting of rice grains, Arkeonews reports.

Wild rice differs from domesticated rice in that the seeds of domesticated rice fall out at maturity, while the mature seeds of domesticated rice remain on the plants. Harvesting rice required some kind of tool; in turn, using a tool meant that early rice farmers selected seeds that tended to stay on the plants. Domestication occurred as the proportion of seeds that remained on the plants increased. Scientists knew that rice began to be domesticated in China around 10,000 B.C., but found the tools with which it was harvested.

Recently, archaeologists found many small pieces of stone with sharp edges that may have been used for harvesting at several Early Neolithic sites in the lower Yangtze River valley. A new study has confirmed that these are indeed tools for harvesting grains. In all, the researchers examined 52 stone tools from the Shanshan and Hehushan sites, which were left by the Shanshan and Quahuqiao cultures. They date from 10,000 to 8,000 years B.C. The stone splinters are rough in appearance and not finely worked but have sharp edges. They are about 4 centimetres wide.

These tools were examined under a microscope. The results showed that 30 of the stones showed signs of wear, similar to those produced by harvesting siliceous (silica-rich) plants, including rice. In addition, 28 of the tools showed chemical traces from regular contact with rice. In addition, rice husks and leaves leave different traces, so it was possible to find out that the collection was carried out by two methods. The first method involved cutting the plant with a sharp edge, like a sickle, while the second method involved cutting the top of the plant by sandwiching it between a finger and a stone.