Developmental plasticity under human management shaped cereal evolution prior to domestication in the Early Holocene southern Levant.

The domestication of plants in southwest Asia was an evolutionary process that took place over several millennia in the Early Holocene. During this time, domestic species developed distinct traits that distinguished them from their wild counterparts. Current models of plant domestication emphasize the role of genetic selection in the evolution of these traits, viewing these as heritable adaptations that arose in response to selective pressures associated with human cultivation. In cereals, domestication resulted in the evolution of nonshattering rachis and increased grain size, two traits that can be tracked directly in the archaeobotanical record. Analyses of Early Neolithic cereal remains demonstrate that grain size increase occurred prior to the evolution of nonshattering rachis, a sequence that is often interpreted as evidence of selection for larger grains under cultivation, specifically tillage. Here, we combine morphological and metrical analyses of cereal remains, stable carbon isotope analysis, and weed ecology to test this hypothesis, using three assemblages from the southern Levant: Pre-Pottery Neolithic A Sharara (