For decades, archaeologists have assumed that one of the earliest signs of this transformation was an increase in cereal grain size. The findings, published in the Proceedings of the National Academy of Sciences, challenge a central assumption about how cereal domestication began. In wild cereals, the rachis fractures as the plant ripens, scattering seeds before people can collect them. The difference suggests that environmental moisture, rather than inherited genetic change, was responsible for much of the early increase in cereal grain size. Subject of Research: The environmental and biological processes that influenced cereal grain size and plant domestication in the Early Holocene southern Levant.