Sickle gloss texture analysis elucidates long-term change in plant harvesting during the transition to agriculture

Archaeobotanical and genetic analysis of modern plant materials are drawing a complex scenario for the origins of cereal agriculture in the Levant. This paper presents an improved method for the study of early farming harvesting systems based on the texture analysis of gloss observed on sickle blades through confocal microscopy. Using this method, we identify different plant harvesting activities (unripe, semi-ripe and ripe cereal reaping and reed and other grass cutting) quantitatively and evaluate their change during the time when plant cultivation activities started and domesticated crops appeared in the Levant (12 800–7000 cal BC). The state of maturity of cereals when harvested shifted over time from unripe, to semi-ripe and finally to ripe. Most of these changes in harvesting techniques are explained by the modification of crops during the transition to agriculture. The shift in plant harvesting strategies was neither chronologically linear nor geographically homogeneous. Fully mature cereal harvesting becomes dominant around 8500 cal BC in the Southern Levant and one millennium later in the Middle Euphrates, which accords with the appearance of domestic varieties in the archaeobotanical record. The change in plant harvesting method fits better with the gradualist model of explanation of cereal agriculture than with the punctual one.