The author studied intensification of plant use (including cereal consumption) during the Natufian period of the Levant, using microscopic analysis of use-wear on 166 basalt grinding stones from Natufian sites. These prehistoric grinding surfaces were compared to those created on an experimental collection of basalt stones used for known tasks. The Natufian tools were judged to have been used for a variety of purposes, including hide working, legume processing, cereal processing, and mineral grinding. There seemed, however, to be a clear increase over time in the use of grinding slabs with flat surfaces, suitable for reducing cereals and legumes to tinier particles, with a,concomitant increase in the release of nutrients. This trend may help explain the appearance of agriculture at the end of the Natufian. (C) 2004 Elsevier Ltd. All rights reserved.